When doing work with real gold leaf a long time ago, it became a common practice to use a red underpaint. That gave a warm glow to the gold, because some of the red actually could be seen. However, if you are using a gold paint that is truly opaque, the color underneath does not make any difference. In that case, what you want is a nice, smooth undercoat. In some brands of paint, some colors are smoother than others, but in most brands, there is no real difference.
