Every time I think I have some sort of ID formula for the white snakes, I see a pic of a known breeding that breaks my rule. You can get closer to exactly what it is if you know how old it is and where in the shed cycle. When they are young they are whiter. As they get closer to shed, they tend to dirty up especially super mojaves. A fresh shed often gives a pinkish animal. Even more info can be had with a black light. I don't have Russo so I can only go by pics on that animal. I do have Phantom, Mojave and Lesser. BEL is hands down my favorite complex and I tend to like them regardless of how white they are. With any luck I should make 20 or 30 blue eyes snakes this year if you include purple passions.
The thing that hasn't been mentioned that can account for visible pattern on a white snake is the possibility of a third gene being involved that can contribute to the darker patches seen on the OP's images.
All that said, I have quite a few BEL complex animals, but oddly enough my whitest animal is actually a super yellow belly which as we all know is an entirely different complex. I have seen a lot of Ivories that are not as white as mine. My point being there is a lot of variation even among animals that have the same morph combinations.