UIColor色のRGB値

(red, green, blue, alpha)

UIColor.gray (0.5, 0.5, 0.5, 1)
UIColor.lightGray (0.666, 0.666, 0.666, 1)
UIColor.darkGray (0.333, 0.333, 0.333, 1)
UIColor.magenta (1, 0, 1, 1)