code: protected FourColors desaturate(FourColors colors) {
          return new FourColors(desaturate(colors.top), desaturate(colors.upperMid), desaturate(colors.lowerMid), desaturate(colors.bottom));
      }
docs: Returns a new FourColors object with each color desaturated using
  {@link desaturate(Color)}.
  
  @param  colors the original colors.
  
  @return the new colors.