Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="gray-darker" style="width:200px;height:200px"></div>
<div class="gray-dark" style="width:200px;height:200px"></div>
<div class="gray" style="width:200px;height:200px"></div>
<div class="gray-light" style="width:200px;height:200px"></div>
<div class="gray-lighter" style="width:200px;height:200px"></div>
<div class="gray-lightest" style="width:200px;height:200px"></div>

SassMeister-input.scss

// ----
// libsass (v3.2.4)
// ----

$gray-base:              #000 !default;
$gray-darker:            lighten($gray-base, 13.5%) !default; // #222
$gray-dark:              lighten($gray-base, 20%) !default;   // #333
$gray:                   lighten($gray-base, 40%) !default; // #666
$gray-light:             lighten($gray-base, 60%) !default; // #999
$gray-lighter:           lighten($gray-base, 80%) !default; // #ccc
$gray-lightest:          lighten($gray-base, 95%) !default; // #f2f2f2

.gray-lightest {
  background-color:$gray-lightest;
  float:left;
}
.gray-darker {
  background-color:$gray-darker;
  float:left;
}
.gray-dark {
  background-color:$gray-dark;
  float:left;
}
.gray {
  background-color:$gray;
  float:left;
}
.gray-light {
  background-color:$gray-light;
  float:left;
}
.gray-lighter {
  background-color:$gray-lighter;
  float:left;
}

SassMeister-output.css

.gray-lightest {
  background-color: #f2f2f2;
  float: left;
}

.gray-darker {
  background-color: #222222;
  float: left;
}

.gray-dark {
  background-color: #333333;
  float: left;
}

.gray {
  background-color: #666666;
  float: left;
}

.gray-light {
  background-color: #999999;
  float: left;
}

.gray-lighter {
  background-color: #cccccc;
  float: left;
}

SassMeister-rendered.html

<div class="gray-darker" style="width:200px;height:200px"></div>
<div class="gray-dark" style="width:200px;height:200px"></div>
<div class="gray" style="width:200px;height:200px"></div>
<div class="gray-light" style="width:200px;height:200px"></div>
<div class="gray-lighter" style="width:200px;height:200px"></div>
<div class="gray-lightest" style="width:200px;height:200px"></div>