You can get a pint of white latex paint at HomeDepot and have it tinted with just a little color. The background above is really faint powder blue. A light back ground bounces more light around in the tank.
In the past, I've had good experience with spraypaint, but considering I'm in a studio apartment not on the ground floor (and dealing with bigger tanks), I'm gong to try the latex paint. When I was in Home Depot, they had these little ~7oz sized trial for a couple dollars, that you can get tinted (I got mine black). container says it should cover a 4x4 area, which should be enough for 2+ coats on most tanks.