Backing paint question

[barry]

I'm doing my first paint job on a RC shell (well, since 1987 anyway). It's very simple - dark blue with a white cross covering the whole shell - kind of like the Scottish flag but with horizontal/vertical white lines rather than diagonals.

Anyway, the blue is turning out a little lighter than I thought. If I spray black over the finished blue, would this darken it a bit? White is going to be my last colour and I was going to back the whole shell with the white as I heard this improves the colours, but I'm now worried it will make the blue even lighter.

One more question - I've put about three coats of the blue on now and it is still very translucent. Do I need to keep applying coats or does paint usually stay translucent until the backing (black or white) is applied?

Cheers,
Barry