MeFoDy

/**
 * Calculate the luminance for a color.
 * See https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-tests
 */
@function luminance($color) {
  $red: nth($linear-channel-values, red($color) + 1);
  $green: nth($linear-channel-values, green($color) + 1);
  $blue: nth($linear-channel-values, blue($color) + 1);

  @return .2126 * $red + .7152 * $green + .0722 * $blue;