Your WordPress WYSIWYG Editor Can Reflect Your Theme Styles - http://amethystwebsitedesign.com/your-wordpress-wysiwyg-editor-can-reflect-your-theme-styles/

editor-style.css

/* Editor Stylesheet for Genesis Sample 2.0.1
--------------------------------------------- */

/* Import Google Fonts */
@import url('//fonts.googleapis.com/css?family=Lato:300,700');

.content {
	color: #666;
	font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
	font-size: 16px;
	font-weight: 300;
	line-height: 1.625;
}

.content a {
	border-bottom: 1px solid #ddd;
	color: #f15123;
}

.content a:hover {
	color: #333;
}

.content p {
	margin: 0 0 26px;
	padding: 0;
}

.content strong {
	font-weight: 700;
}

.content ol,
.content ul {
	margin: 0 0 26px 40px;
	padding: 0;
}

.content ol li {
	list-style-type: decimal;
}

.content ul li {
	list-style-type: disc;
}

.content ol ol,
.content ul ul {
	margin-bottom: 0;
}

.content blockquote,
.content blockquote::before {
	color: #999;
}

.content blockquote {
	margin: 40px 40px 24px;
}

.content blockquote::before {
	content: "\201C";
	display: block;
	font-size: 30px;
	height: 0;
	left: -20px;
	position: relative;
	top: -10px;
}

.content cite {
	font-style: normal;
}

/* Headings
--------------------------------------------- */
.content h1,
.content h2,
.content h3,
.content h4,
.content h5,
.content h6 {
	color: #333;
	font-family: 'Lato', sans-serif;
	font-weight: 700;
	line-height: 1.2;
	margin: 0 0 16px;
}

.content h1 {
	font-size: 36px;
}

.content h2 {
	font-size: 30px;
}

.content h3 {
	font-size: 24px;
}

.content h4 {
	font-size: 20px;
}

.content h5 {
	font-size: 18px;
}

.content h6 {
	font-size: 16px;
}

/* Tables
--------------------------------------------- */
.content table {
	border-collapse: collapse;
	border-spacing: 0;
	line-height: 2;
	margin-bottom: 40px;
	width: 100%;
}

.content tbody {
	border-bottom: 1px solid #ddd;
}

.content th,
.content td {
	text-align: left;
}

.content th {
	font-weight: bold;
	text-transform: uppercase;
}

.content td {
	border-top: 1px solid #ddd;
	padding: 6px 0;
}

/*
Common Classes
---------------------------------------------------------------------------------------------------- */
.content img.centered,
.content .aligncenter {
	display: block;
	margin: 0 auto 24px;
}

.content img.alignnone {
	margin-bottom: 12px;
}

.content .alignleft {
	float: left;
	text-align: left;
}

.content .alignright {
	float: right;
	text-align: right;
}

.content img.alignleft,
.content .wp-caption.alignleft {
	margin: 0 24px 24px 0;
}

.content img.alignright,
.content .wp-caption.alignright {
	margin: 0 0 24px 24px;
}

.content .wp-caption-text {
	font-size: 14px;
	font-weight: 700;
	text-align: center;
}

/* Column Classes
	Link: http://twitter.github.io/bootstrap/assets/css/bootstrap-responsive.css
--------------------------------------------- */
.five-sixths,
.four-sixths,
.one-fourth,
.one-half,
.one-sixth,
.one-third,
.three-fourths,
.three-sixths,
.two-fourths,
.two-sixths,
.two-thirds {
	box-shadow: inset 0 0 0 1px #ddd;
	float: left;
	margin-left: 2.564102564102564%;
}

.one-half,
.three-sixths,
.two-fourths {
	width: 48.717948717948715%;
}

.one-third,
.two-sixths {
	width: 31.623931623931625%;
}

.four-sixths,
.two-thirds {
	width: 65.81196581196582%;
}

.one-fourth {
	width: 23.076923076923077%;
}

.three-fourths {
	width: 74.35897435897436%;
}

.one-sixth {
	width: 14.52991452991453%;
}

.five-sixths {
	width: 82.90598290598291%;
}

.first {
	clear: both;
	margin-left: 0;
}

functions.php

<?php
//* Do NOT include the opening php tag
// Add the code below to the functions.php of your child theme

// Customize Visual Editor
add_editor_style();