As mentioned, Sass specifically comes equipped with functions that make working with colors easier.

The alpha parameter in a color like RGBA or HSLA is a mask denoting opacity. It specifies how one color should be merged with another when the two are on top of each other.

• In Sass, the function fade-out makes a color more transparent by taking a number between 0 and 1 and decreasing opacity, or the alpha channel, by that amount:

   $color: rgba(39, 39, 39, 0.5);
   $amount: 0.1;
   $color2: fade-out($color, $amount);//rgba(39, 39, 39, 0.4) 

• The fade-in color function changes a color by increasing its opacity:

  $color: rgba(55,7,56, 0.5);
  $amount: 0.1;
  $color2: fade-in($color, $amount); //rgba(55,7,56, 0.6)

• The function adjust-hue($color, $degrees) changes the hue of a color by taking color and a number of degrees (usually between -360 degrees and 360 degrees), and rotate the color wheel by that amount.