I used to carry a white bag too which I diligently cleaned each time I finished my game. And, since I used to play in the 'tropics,' the bag (and clubs etc) would get dirty quickly. I simply used warm water and some soap. I also used a cleaning solvent which was available at most hardware stores (I can't recall what it's called).
After a few months, I just gave up. It was too much trouble and no matter how much cleaning I did, the bag never quite looked the same. Now I carry a dark blue Callaway bag. Stains schmains :P