Complex theming through custom string interpolation of map variables in Sass https://twitter.com/stowball/status/870245991663804416

functions|_color.scss

@function color($keys, $function-name: "color") {
  @return get($colors, $keys, $function-name);
}

@function c($keys) {
  @return color($keys, "c");
}

functions|_get.scss

@function get($original-map, $keys: null, $stack-trace-name: null) {
  $map: $original-map;

  @if ($keys) {
    @each $key in $keys {
      $map: map-get($map, $key);
    }
  }

  @if ($map == null) {
    $error: log-error("No map found for #{unquote($stack-trace-name)}(#{$keys}). Map contains #{$original-map}");
  }

  @return $map;
}

functions|_log-error.scss

@function log-error($message) {
  $message: "***** " + $message + " *****";

  @warn $message;
  @error $message;

  @return null;
}

mixins|_theme.scss

@mixin theme($css-property, $css-value, $theme-classes: t) {
  @each $selector in & {
    @each $class in $theme-classes {
      @each $theme, $theme-properties in c(themes) {
        $value: $css-value;

        @each $theme-name, $theme-value in $theme-properties {
          $rgba-value: "rgba(#{red($theme-value)}, #{green($theme-value)}, #{blue($theme-value)}";
          $value: str-replace($value, "rgba(${#{$theme-name}}", $rgba-value);
          $value: str-replace($value, "${#{$theme-name}}", $theme-value);
        }

        @at-root .#{$class}-#{join($theme, $selector)} {
          #{$css-property}: unquote($value);
        }
      }
    }
  }
}

settings|_colors.scss

$colors: (
  themes: (
    nrl: (
      primary: #1d3c34,
      tint: #142c25,
      tint-rm: #0b1c17,
      secondary: #006c3c,
      highlight: #fedb00,
    ),
    broncos: (
      primary: #6c1d45,
      tint: #521633,
      tint-rm: #3d0d21,
      secondary: #92426b,
      highlight: #f8cc0d,
    ),
    bulldogs: (
      primary: #00468b,
      tint: #00306f,
      tint-rm: #001843,
      secondary: #0072bc,
      highlight: #0090f0,
    ),
  )
);