colors.sass

// ...
$color-variation: 10%

$color-set-1:     $dark-violet $dark-green $orange
$color-set-2:     $gray $bright-violet $bright-green
$color-set-3:     $turquoise $yellow $red

$color-sets:      $color-set-1 $color-set-2 $color-set-3

=color($property: color, $level: 1, $variation: 0)
  @for $i from 1 through length($color-sets)
    $set  : nth($color-sets, $i)
    $color: nth($set, $level)

    @if $variation != 0
      @if $variation > 0
        $color: lighten($color, $color-variation * $variation)
      @else
        $color: darken($color, $color-variation * $variation)

    // default
    @if $i == 1
      #{$property}: $color

    @else
      html.color-set-#{$i} &
        #{$property}: $color