The CMYK controls are provided only to ease the input of colour values using CMYK notation. If you select RGB, the initials of the three colours will appear and you can set the colour from 0 to 255 with the spin button.
如果选择的是 RGB，您就能够看到选值框旁边的三个颜色的缩写字母。借助这个选值框就可以按百分比来设置颜色比例。