I have painted a ton of rigs (mediocre jobs at best), and I can say that white is without a boubt, the most forgiving color to work with. A light yellow would probably be pretty good as well. Wait, I have a car that is white and yellow, and the paint doesnt look nearly as bad as it really is - especially in the sunlight.
As for flats, I can say that they are a bitch to clean - you basically can't do it (my Zebaru was striped with flat white and black).
If you are looking for cheap, just go down to the hardware store, spend ten bucks on a quart of enamel, and spray it on. Looks better than a rattle can job, and is a bunch cheaper. I sprayed my second subaru with Rustoleum tan I think, and it still looks okay seven years later. I only used a quart of paint - $7.99 (XJ might take two). When the color starts to fade, pick another color and do it again...
Travis