Color palette implementation in Sass

color.scss

// Color scale function
// ====================
//
// Similarly to dirg, this assists with creating rhythmic colour
// variations from a palette. The definition of the $color-palette var
// is made at build time.

// Granularity of variations.
$step-size: 7.5% !default;

// Alternatively, define this in a separate file.
$color-palette: (
  'first': #000000,
  'second': #FFFFFF,
  'third': #D92C26
) !default;

// Example:
// 
// .FooComponent {
//   background: color('first');
//   color: color('second', 2);
// }
@function color($name, $scale: 0) {
  @if ($scale > 5 or $scale < (-5)) {
    @error 'Scale argument cannot be #{$scale}. Passed with #{$name}';
  }

  $val: map-get($color-palette, $name);

  @if $val {
    @if $scale < 0 {
      @return mix(white, $val, abs($scale) * $step-size);
    } @else {
      @return mix(black, $val, $scale * $step-size);
    }
  } @else {
    @error 'Couldn\'t find color with name #{$name}';
  }
}