Actually, the change from dark earth and dark green to ocean grey and dark green was more due to the fact that as RAF aircraft were on the offensive they were also flying at higher altitudes, and the dark earth was of no value at all. I used to think it was down to wanting less visibility over the sea as well until I read otherwise.
I'll have to look the reference up. There is a lot more to it than just flying higher but without the book to hand I can't say much more about it.
Sorry, back on topic.