code: function create(r, g, b, a) {
    return [r || 0, g || 0, b || 0, (a === undefined) ? 1 : a];
  }
docs: RGBA color constructor function
  @param  {Number} [r=0] - red component (0..1)
  @param  {Number} [g=0] - green component (0..1)
  @param  {Number} [b=0] - blue component (0..1)
  @param  {Number} [a=1] - alpha component (0..1)
  @return {Array}  - RGBA color array [r,g,b,a] (0..1)