white white white.
Oil paints are semi-transparent, so you would be well-off to leave the canvas white.White canvas allows the most light to be refracted through layers of paint.
Many people were taught in school to put down a thin wash, but that is really just a training wheel, in my opinion, to help you mix colors & values more accurately.
If you already know how to mix colors and have done a few decent paintings, you'll find that a plain white canvas will give you the most colorful results.
