It stays whichever color you select, and it turns on in that color when you turn on the lights. You can also turn it on manually without the lights, but if you leave it on, that's the color it returns to when you turn on the headlights. Or it stays off if that's the "color" you pick.
The problem is, it's too bright. The lights under the front and rear footwells are nice and dim, but the cupholder lights distract your eyes in the dark. I wish you could control the brightness, and that maybe there was a really dim one under the dash or something.
Hope that made sense.