modified version of flatdoc/theme-white/style.css for dark contrasting menus and blockquotes

style.css

/*

Please don't edit this file directly.
Instead, edit the stylus (.styl) files and compile it to CSS on your machine.

*/
/* ----------------------------------------------------------------------------
 * Fonts
 */
@import url("//fonts.googleapis.com/css?family=Montserrat:700|Open+Sans:300");
/* ----------------------------------------------------------------------------
 * Base
 */
html,
body,
div,
span,
applet,
object,
iframe,
h1,
h2,
h3,
h4,
h5,
h6,
p,
blockquote,
pre,
a,
abbr,
acronym,
address,
big,
cite,
code,
del,
dfn,
em,
img,
ins,
kbd,
q,
s,
samp,
small,
strike,
strong,
sub,
sup,
tt,
var,
dl,
dt,
dd,
ol,
ul,
li,
fieldset,
form,
label,
legend,
table,
caption,
tbody,
tfoot,
thead,
tr,
th,
td {
  margin: 0;
  padding: 0;
  border: 0;
  outline: 0;
  font-weight: inherit;
  font-style: inherit;
  font-family: inherit;
  font-size: 100%;
  vertical-align: baseline;
}
body {
  line-height: 1;
  color: #000;
  background: #fff;
}
ol,
ul {
  list-style: none;
}
table {
  border-collapse: separate;
  border-spacing: 0;
  vertical-align: middle;
}
caption,
th,
td {
  text-align: left;
  font-weight: normal;
  vertical-align: middle;
}
a img {
  border: none;
}
html,
body {
  height: 100%;
}
html {
  overflow-x: hidden;
}
body,
td,
textarea,
input {
  font-family: Helvetica Neue, Open Sans, sans-serif;
  line-height: 1.6;
  font-size: 13px;
  color: #111111;
}
@media (max-width: 480px) {
  body,
  td,
  textarea,
  input {
    font-size: 12px;
  }
}
a {
  color: #33AACC;
  text-decoration: none;
}
a:hover {
  color: #33AACC;
}
/* ----------------------------------------------------------------------------
 * Content styling
 */
.content p,
.content ul,
.content ol,
.content h1,
.content h2,
.content h3,
.content h4,
.content h5,
.content h6,
.content pre,
.content blockquote {
  padding: 10px 0;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}
.content h1,
.content h2,
.content h3,
.content h4,
.content h5,
.content h6 {
  font-weight: bold;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
.content pre {
  font-family: Menlo, monospace;
}
.content ul > li {
  list-style-type: disc;
}
.content ol > li {
  list-style-type: decimal;
}
.content ul,
.content ol {
  margin-left: 20px;
}
.content ul > li {
  list-style-type: none;
  position: relative;
}
.content ul > li:before {
  content: '';
  display: block;
  position: absolute;
  left: -17px;
  top: 7px;
  width: 5px;
  height: 5px;
  -webkit-border-radius: 4px;
  border-radius: 4px;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
  background: #fff;
  border: solid 1px #EEEEEE;
}
.content li > :first-child {
  padding-top: 0;
}
.content strong,
.content b {
  font-weight: bold;
}
.content i,
.content em {
  font-style: italic;
}
.content code {
  font-family: Menlo, monospace;
  background: #272724;
  padding: 1px 3px;
  font-size: 0.95em;
}
.content pre > code {
  display: block;
  background: transparent;
  font-size: 0.85em;
  letter-spacing: -1px;
}
.content blockquote :first-child {
  padding-top: 0;
}
.content blockquote :last-child {
  padding-bottom: 0;
}
.content table {
  margin-top: 10px;
  margin-bottom: 10px;
  padding: 0;
  border-collapse: collapse;
  clear: both;
  float: left;
}
.content table tr {
  border-top: 1px solid #ccc;
  background-color: #fff;
  margin: 0;
  padding: 0;
}
.content table tr :nth-child(2n) {
  background-color: #f8f8f8;
}
.content table tr th {
  text-align: auto;
  font-weight: bold;
  border: 1px solid #ccc;
  margin: 0;
  padding: 6px 13px;
}
.content table tr td {
  text-align: auto;
  border: 1px solid #ccc;
  margin: 0;
  padding: 6px 13px;
}
.content table tr th :first-child,
.content table tr td :first-child {
  margin-top: 0;
}
.content table tr th :last-child,
.content table tr td :last-child {
  margin-bottom: 0;
}
/* ----------------------------------------------------------------------------
 * Content
 */
.content-root {
  min-height: 90%;
  position: relative;
}
.content {
  padding-top: 30px;
  padding-bottom: 40px;
  padding-left: 40px;
  padding-right: 40px;
  zoom: 1;
  max-width: 700px;
}
.content:before,
.content:after {
  content: "";
  display: table;
}
.content:after {
  clear: both;
}
.content blockquote {
  color: #33AACC;
}

.content h1,
.content h2,
.content h3 {
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  font-family: montserrat;
  padding-bottom: 0;
    color: #000000;
}
.content h1 + p,
.content h2 + p,
.content h3 + p,
.content h1 ul,
.content h2 ul,
.content h3 ul,
.content h1 ol,
.content h2 ol,
.content h3 ol {
  padding-top: 10px;
}
.content h1,
.content h2 {
  text-transform: uppercase;
  letter-spacing: 1px;
  font-size: 1.5em;
}
.content h3 {
  font-size: 1.2em;
}
.content h1,
.content h2,
.content .big-heading,
body.big-h3 .content h3 {
  padding-top: 80px;
}
.content h1:before,
.content h2:before,
.content .big-heading:before,
body.big-h3 .content h3:before {
  display: block;
  content: '';
  background: -webkit-linear-gradient(left, #dfe2e7 80%, rgba(223,226,231,0));
  background: -moz-linear-gradient(left, #dfe2e7 80%, rgba(223,226,231,0));
  background: -o-linear-gradient(left, #dfe2e7 80%, rgba(223,226,231,0));
  background: -ms-linear-gradient(left, #dfe2e7 80%, rgba(223,226,231,0));
  background: linear-gradient(to right, #dfe2e7 80%, rgba(223,226,231,0));
  -webkit-box-shadow: 0 1px 0 rgba(255,255,255,0.4);
  box-shadow: 0 1px 0 rgba(255,255,255,0.4);
  height: 1px;
  position: relative;
  top: -40px;
  left: -40px;
  width: 100%;
}
@media (max-width: 768px) {
  .content h1,
  .content h2,
  .content .big-heading,
body.big-h3 .content h3 {
    padding-top: 40px;
  }
  .content h1:before,
  .content h2:before,
  .content .big-heading:before,
body.big-h3 .content h3:before {
    background: #dfe2e7;
    left: -40px;
    top: -20px;
    width: 120%;
  }
}
.content h4,
.content h5,
.content .small-heading,
body:not(.big-h3) .content h3 {
  border-bottom: solid 1px rgba(0,0,0,0.07);
  color: #000000;
  padding-top: 30px;
  padding-bottom: 10px;
}
body:not(.big-h3) .content h3 {
  font-size: 0.9em;
}
.content h1:first-child {
  padding-top: 0;
}
.content h1:first-child,
.content h1:first-child a,
.content h1:first-child a:visited {
  color: #33AACC;
}
.content h1:first-child:before {
  display: none;
}
@media (max-width: 768px) {
  .content h4,
  .content h5,
  .content .small-heading,
  body:not(.big-h3) .content h3 {
    padding-top: 20px;
  }
}
@media (max-width: 480px) {
  .content {
    padding: 20px;
    padding-top: 40px;
  }
  .content h4,
  .content h5,
  .content .small-heading,
  body:not(.big-h3) .content h3 {
    padding-top: 10px;
  }
}
body.no-literate .content pre > code {
  background: #272724;
  border: solid 1px #e7eaee;
  border-top: solid 1px #dbdde2;
  border-left: solid 1px #e2e5e9;
  display: block;
  padding: 10px;
  -webkit-border-radius: 2px;
  border-radius: 2px;
  overflow: auto;
}
body.no-literate .content pre > code {
  -webkit-overflow-scrolling: touch;
}
body.no-literate .content pre > code::-webkit-scrollbar {
  width: 15px;
  height: 15px;
}
body.no-literate .content pre > code::-webkit-scrollbar-thumb {
  background: #ddd;
  -webkit-border-radius: 8px;
  border-radius: 8px;
  border: solid 4px #272724;
}
body.no-literate .content pre > code:hover::-webkit-scrollbar-thumb {
  background: #999;
}
@media (max-width: 1180px) {
  .content pre > code {
    background: #272724;
    border: solid 1px #e7eaee;
    border-top: solid 1px #dbdde2;
    border-left: solid 1px #e2e5e9;
    display: block;
    padding: 10px;
    -webkit-border-radius: 2px;
    border-radius: 2px;
    overflow: auto;
  }
  .content pre > code {
    -webkit-overflow-scrolling: touch;
  }
  .content pre > code::-webkit-scrollbar {
    width: 15px;
    height: 15px;
  }
  .content pre > code::-webkit-scrollbar-thumb {
    background: #ddd;
    -webkit-border-radius: 8px;
    border-radius: 8px;
    border: solid 4px #272724;
  }
  .content pre > code:hover::-webkit-scrollbar-thumb {
    background: #999;
  }
}
.button {
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  font-family: montserrat, sans-serif;
  letter-spacing: -1px;
  font-weight: bold;
  display: inline-block;
  padding: 3px 25px;
  border: solid 2px #33AACC;
  -webkit-border-radius: 20px;
  border-radius: 20px;
  margin-right: 15px;
}
.button,
.button:visited {
  background: #272724;
  color: #fff;
  text-shadow: none;
}
.button:hover {
  border-color: #33AACC;
  background: #33AACC;
  color: #fff;
}
.button.light,
.button.light:visited {
  background: #272724;
  color: #fff;
  border-color: #33AACC;
  text-shadow: none;
}
.button.light:hover {
  border-color: #33AACC;
  background: #33AACC;
  color: #fff;
}
.content .button + em {
  color: #EEEEEE;
}
@media (min-width: 1180px) {
  body:not(.no-literate) .content-root {
    background-color: #272724;
    -webkit-box-shadow: inset 780px 0 #fff, inset 781px 0 #dfe2e7, inset 790px 0 5px -10px rgba(0,0,0,0.1);
    box-shadow: inset 780px 0 #fff, inset 781px 0 #dfe2e7, inset 790px 0 5px -10px rgba(0,0,0,0.1);
  }
}
@media (min-width: 1180px) {
  body:not(.no-literate) .content {
    padding-left: 0;
    padding-right: 0;
    width: 930px;
    max-width: none;
  }
  body:not(.no-literate) .content > p,
  body:not(.no-literate) .content > ul,
  body:not(.no-literate) .content > ol,
  body:not(.no-literate) .content > h1,
  body:not(.no-literate) .content > h2,
  body:not(.no-literate) .content > h3,
  body:not(.no-literate) .content > h4,
  body:not(.no-literate) .content > h5,
  body:not(.no-literate) .content > h6,
  body:not(.no-literate) .content > pre,
  body:not(.no-literate) .content > blockquote {
    width: 550px;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    padding-right: 40px;
    padding-left: 40px;
  }
  body:not(.no-literate) .content > h1,
  body:not(.no-literate) .content > h2,
  body:not(.no-literate) .content > h3 {
    clear: both;
    width: 100%;
  }
  body:not(.no-literate) .content > pre,
  body:not(.no-literate) .content > blockquote {
    width: 380px;
    padding-left: 20px;
    padding-right: 20px;
    float: right;
    clear: right;
  }
  body:not(.no-literate) .content > pre + p,
  body:not(.no-literate) .content > blockquote + p,
  body:not(.no-literate) .content > pre + ul,
  body:not(.no-literate) .content > blockquote + ul,
  body:not(.no-literate) .content > pre + ol,
  body:not(.no-literate) .content > blockquote + ol,
  body:not(.no-literate) .content > pre + h4,
  body:not(.no-literate) .content > blockquote + h4,
  body:not(.no-literate) .content > pre + h5,
  body:not(.no-literate) .content > blockquote + h5,
  body:not(.no-literate) .content > pre + h6,
  body:not(.no-literate) .content > blockquote + h6 {
    clear: both;
  }
  body:not(.no-literate) .content > p,
  body:not(.no-literate) .content > ul,
  body:not(.no-literate) .content > ol,
  body:not(.no-literate) .content > h4,
  body:not(.no-literate) .content > h5,
  body:not(.no-literate) .content > h6 {
    float: left;
    clear: left;
  }
  body:not(.no-literate) .content > h4,
  body:not(.no-literate) .content > h5,
  body:not(.no-literate) .content > .small-heading,
  body:not(.big-h3) body:not(.no-literate) .content > h3 {
    margin-left: 40px;
    width: 470px;
    margin-bottom: 3px;
    padding-left: 0;
    padding-right: 0;
  }
  body:not(.no-literate) .content > table {
    margin-left: 40px;
    margin-right: 40px;
    max-width: 470px;
  }
  body:not(.no-literate):not(.big-h3) .content > h3 {
    margin-left: 40px;
    width: 470px;
    margin-bottom: 3px;
    padding-left: 0;
    padding-right: 0;
  }
}
.header {
  background: #272724;
  border-bottom: solid 1px #dfe2e7;
  padding: 15px 15px 15px 30px;
  zoom: 1;
  line-height: 20px;
  position: relative;
}
.header:before,
.header:after {
  content: "";
  display: table;
}
.header:after {
  clear: both;
}
.header .left {
  float: left;
}
.header .right {
  text-align: right;
  position: absolute;
  right: 15px;
  top: 15px;
}
.header .right iframe {
  display: inline-block;
  vertical-align: middle;
}
.header h1 {
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  font-weight: bold;
  font-family: montserrat, sans-serif;
  font-size: 13px;
}
.header h1,
.header h1 a,
.header h1 a:visited {
  color: #EEEEE;
}
.header h1 a:hover {
  color: #FFFFFF;
}
.header li a {
  font-size: 0.88em;
  color: #EEEEEE;
  display: block;
}
.header li a:hover {
  color: #FFFFFF;
}
@media (min-width: 480px) {
  .header h1 {
    float: left;
  }
  .header ul,
  .header li {
    display: block;
    float: left;
  }
  .header ul {
    margin-left: -15px;
  }
  .header h1 + ul {
    border-left: solid 1px #EEEEEE;
    margin-left: 15px;
  }
  .header li {
    border-left: solid 1px rgba(255,255,255,0.5);
    border-right: solid 1px #dfe2e7;
  }
  .header li:last-child {
    border-right: 0;
  }
  .header li a {
    padding: 0 15px;
  }
}
@media (max-width: 480px) {
  .right {
    display: none;
  }
}
.menubar {
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
.menubar .section {
  padding: 30px 30px;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}
.menubar .section + .section {
  border-top: solid 1px #dfe2e7;
}
.menubar .section.no-line {
  border-top: 0;
  padding-top: 0;
}
a.big.button {
  display: block;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
  width: 100%;
  padding: 10px 20px;
  text-align: center;
  font-weight: bold;
  font-size: 1.1em;
  background: transparent;
  border: solid 3px #33AACC;
  -webkit-border-radius: 30px;
  border-radius: 30px;
  font-family: montserrat, sans-serif;
}
a.big.button,
a.big.button:visited {
  color: #fff;
  text-decoration: none;
}
a.big.button:hover {
  background: #33AACC;
}
a.big.button:hover,
a.big.button:hover:visited {
  color: #fff;
}
@media (max-width: 480px) {
  .menubar {
    padding: 20px;
    border-bottom: solid 1px #dfe2e7;
  }
}
@media (max-width: 768px) {
  .menubar {
    display: none;
  }
}
@media (min-width: 768px) {
  .content-root {
    padding-left: 230px;
  }
  .menubar {
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 230px;
    border-right: solid 1px #dfe2e7;
  }
  .menubar.fixed {
    position: fixed;
    overflow-y: auto;
  }
  .menubar.fixed {
    -webkit-overflow-scrolling: touch;
  }
  .menubar.fixed::-webkit-scrollbar {
    width: 15px;
    height: 15px;
  }
  .menubar.fixed::-webkit-scrollbar-thumb {
    background: #272724;
    -webkit-border-radius: 8px;
    border-radius: 8px;
    border: solid 4px #fff;
  }
  .menubar.fixed:hover::-webkit-scrollbar-thumb {
    background: #999;
  }
}
.menubar {
  font-size: 0.9em;
  background: #272724;
}
.menu ul.level-1 > li + li {
  margin-top: 20px;
}
.menu a {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
  position: relative;
  display: block;
  padding-top: 1px;
  padding-bottom: 1px;
  margin-right: -30px;
}
.menu a,
.menu a:visited {
  color: #EEEEEE;
}
.menu a:hover {
  color: #FFFFFF;
}
.menu a.level-1 {
  font-family: montserrat, sans-serif;
  text-transform: uppercase;
  font-size: 0.9em;
  font-weight: bold;
}
.menu a.level-1,
.menu a.level-1:visited {
  color: #EEEEEE;
}
.menu a.level-1:hover {
  color: #FFFFFF;
}
.menu a.level-2 {
  font-weight: normal;
}
.menu a.level-3 {
  font-weight: normal;
  font-size: 0.9em;
  padding-left: 10px;
}
.menu a.active {
  font-weight: bold !important;
}
.menu a.active,
.menu a.active:visited,
.menu a.active:hover {
  color: #33AACC !important;
}
.menu a.active:after {
  content: '';
  display: block;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
  position: absolute;
  top: 10px;
  right: 30px;
  width: 9px;
  height: 3px;
  -webkit-border-radius: 2px;
  border-radius: 2px;
  background: #272724;
}

code { color: #EFEFEF; }
code .string,
code .number {
  color: #3ac;
}
code .init {
  color: #383;
}
code .keyword {
  font-weight: bold;
}
code .comment {
  color: #FFE000;
}
.large-brief .content > h1:first-child + p,
.content > p.brief {
  font-size: 1.3em;
  font-family: Open Sans, sans-serif;
  font-weight: 300;
}
.title-area {
  min-height: 100px;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  text-align: center;
  border-bottom: solid 1px #dfe2e7;
  overflow: hidden;
}
.title-area > img.bg {
  z-index: 0;
  position: absolute;
  left: -9999px;
}
.title-area > div {
  position: relative;
  z-index: 1;
}

Modify the Flatdoc default theme template:

  <!-- Flatdoc theme -->
  <link  href='https://cdn.rawgit.com/meoso/930d2a11118f7901c4be65fc90de18b2/raw/6bc2e17b3d411a5ba007bd60f3dcfded4fc9943a/style.css' rel='stylesheet'>
  <script src='https://cdn.rawgit.com/rstacruz/flatdoc/v0.9.0/theme-white/script.js'></script>