@function contrast ($hex) {
  $color: 0;
  $red: red($hex);
  $green: green($hex);
  $blue: blue($hex);
  $threshold: 0.5;
  $borderThreshold: 0.8;

  $background: rgb($red, $green, $blue);

  $r: $red * 0.2126;
  $g: $green * 0.7152;
  $b: $blue * 0.0722;

  $sum: $r + $g + $b;

  $percievedLightness: $sum / 255;

  $color: hsl(0, 0%, (($percievedLightness - $threshold) * -10000000%));
  @return $color;
}