Using lists like a hash in Sass

That's right, you can use Sass lists like an associative array!

In this example we're basically creating a comma-separated list of space-separated lists (zomg). Here's the mixin (with some extra logic to take an "after" argument that creates a pseudo-element. You know, just for fun):

@mixin category-colors($after: false)
  @each $category in $categories
    @if $after == true
      .cat-#{nth($category, 1)}:after
        background-color: nth($category, 2)

    @else
      .cat-#{nth($category, 1)}
        background-color: nth($category, 2)

Pretty crazy, right? CRAZY AWESOME.

See a full usage example with CSS output in this GitHub gist