def fade(color, factor)
      new_alpha = int8_mult(a(color), factor)
      (color & 0xffffff00) | new_alpha
    end
def fade(color, factor)
      new_alpha = int8_mult(a(color), factor)
      (color & 0xffffff00) | new_alpha
    end
Lowers the intensity of a color, by lowering its alpha by a given factor.
 @param [Integer] color The color to adjust.
 @param [Integer] factor Fade factor as an integer between 0 and 255.
 @return [Integer] The faded color.