code: function setRGB(color, r, g, b, a) {
      color[0] = r;
      color[1] = g;
      color[2] = b;
      color[3] = (a !== undefined) ? a : 1;
  
      return color;
  }
docs: Updates a color based on r, g, b, a component values
  @param  {Array} color   - RGBA color array [r,g,b,a] to update
  @param  {Number} r      - red component (0..1)
  @param  {Number} g      - green component (0..1)
  @param  {Number} b      - blue component (0..1)
  @param  {Number} [a=1]  - alpha component (0..1)
  @return {Array} - updated RGBA color array [r,g,b,a] (0..1)