My guess: You can remove the tires for flight, paint adds weight and I don't see the Russian army scraping off the current paint without fucking up the primer/anti corrosion layer.
Light paint keeps the heat away, so it's the default. Plus, this entire kerfuffle has been a matter class in lack of planning. They never thought they would need it, so why bother painting 50+ year old planes another color.
In the case of strategic bombers, anti-flash white is a key feature to reflect as much of the thermal pulse of a nuclear detonation as possible; theoretically you want these planes to survive the apocalypse that they're unleashing to return to base and do it again.