Not really, doing a color and black white version of movies like this is becoming pretty common these day. They've done it with Mad Max: Fury Road, Werewolf by Night, and I'm pretty sure there are at least one or two others I can't think of right now.
I don't see why they would, it wasn't really going for that kind of feel. Most of time when they do this kind of thing, it's because they're mimicking a certain style, and Fallout really wasn't doing that.
And the present day stuff in Fallout is still set on Earth, it's just after a big nuclear war destroyed most of the pre-bombs civilization.