A darker interior is actually easier to keep clean. I read that the latte interior shows dirt very easily.
If you are referring to the exterior - there is no way around it, a dark exterior stays clean for 1 day after you wax the car. But that one day - oh man, its nice! The trick to keeping a dark car looking clean is to use polish before you wax (its a different product). The polish will really bring out the gloss and luster of the paint, then you cover it with a coat of good carnuba wax. Even if the car gets dirty, it might not be clean, but the gloss will show through. I've had people comment "great shine" when I thougth the car was filthy. I then realized they were commenting on the overall gloss of the car, which made the dirt less noticable.
If you enjoy taking care of your car, then get a dark exterior with light interior. If you wash your car twice a year, get a light exterior with dark interior.