Too me it has just always made sense for Dagobah to be white. It is an extremely boggy planet. Every scene we see on the planet, we have a massive amount of fog. With so much fog there would be no greenish tint. Planet isn't even that green, it is more brown like. I would have always expected a clear Dagobah to look more brown like than green like from space, perhaps more of a nasty brownish puke green than anything else. When I saw Dagobah on the ROTS deleted scene I could not help but think it was WAY too green.

But seriously, when flying over the ocean in an airplane on a cloudy day, how much of a "blue" tint do you see the clouds having due to the ocean down there under them someplace? You don't, you see a sheet of white. When they originally made it white, they had that in mind, and I feel they knew what they were doing. I have always imagined Dagobah having a pretty constant fog covering all the time, and everything we see in ESB seems to support this. Also, I that bluish tint as the atmosphere of the planet has been universal, every planet in the OT has that if I am not mistaken.

Out of all the complaints I have heard about ESB over the years, "All the dang planets look exactly alike!" has never been one of them.