/// Create a grayscale color range 0-100 with optional alpha value
/// @param {Number} $value [50] range [0, 100]
/// @param {Number} $alpha [1] range [0, 1]
/// @return {Color} rgba color
/// @link http://codepen.io/Lokua/pen/zxKQWG?editors=110
/// @group color
@function o-gray($value: 50, $alpha: 1) {
  $x: round(($value / 100) * 255);
  @return rgba($x, $x, $x, $alpha);
}

/// @alias o-gray
@function o-grey($value, $alpha) {
  @return o-gray($value, $alpha);
}