Iain, a very good friend of mine (a fellow woodie of course) was painted dark blue one season. They made an excellent job as well, you could have shaved in the shine. Anyway, after launching all was well for a couple of months then the sun got out proper and heated the planking up so much above the waterline she opened up good and proper. You could wave to people through the gaps!!
Then it rained. The rain ran off the decks, down the hull, through the gaps and into every bed, cupboard, wardrobe... you get the idea. Next season she was back in white!