I have the MaxxAir FanMate over my Fantastic Fan, a white one. It is in the rear bedroom and I thought that with the grey cover on the Fantastic Fan it would be enough. If I had to do it again I think I would at least go with the dark one to cut down the light some. I also have 3 other MaxxAir covers that are white so I wanted them to match. But in hind sight I don't think it matters, as a matter of fact it might look good up there.
I did see a RV at my local CW that had one this way with the others white on a white roof and it looked rather unique, I liked it and thought, why didn't I do that.
It works great and I like the fact that it is hinged so it can be cleaned if necessary.