You might see engine blocks painted. Even valve covers. But, it isn't all that often that you actually see heads painted. Like others have mentioned, the heat will pop that stuff off in what I would imagine would be just a few long rides. Just my $.02
You MIGHT be able to get it powder coated a certain color. Or maybe even anodized. But, that's something that you'll have to look into. I would be concerned about tolerances and such of the head being disturbed if it were dipped.