It's nothing new really. Here's the explanation:
- SU 34 has a daytime camo paint job for daytime operations;
- SU 35BM has a nightime camo paint job for nightime operations.
It is a practice used by the airforces since ww2. Though the new aircraft tech makes this practice rather obsolete. For example the US uses a shade of
grey for both daytime and nightime operations, it blends in perfectly with the scenery. Plus some composite materials these days are impossible to
paint. Painting them in anything else then radar absorbing paint would make them targets, so SU 34 is constructed on old technology
there is a lot
in one picture