Base coats DO make a difference. A silver base will give a brighter, colder look, while a gold base will warm the color. A darker base will accent the metallic nature of the paint, but will deepen the color. In an effort to deepen candy red paintjobs in the '60s, it was sometimes sprayed over an apple green base... making it a duller red until direct sunlight shone on it, and those sections would gleam true red.