I thin on a colour like Habby, black, red, blue, the darker colours, I would leave them silver. In my case, I had the same wheels on my wifes' Rallye Red Si and they looked sweet. Refer to the pic I posted in the o/p's other thread. The wife's car is gone now and I have the wheels on my Taffy white Si and they just don't look as good as they did on the red car. I was thinking of powder coating mine also.
Something like this.
You can see from the colour of the centre cap, that they are not much darker. I don't know what colour it is, but it's very similar to the 04-05 RSX Type-S wheel colour. I like them I think they would look very nice on my white car.