Yes, you can feed them the same diet.
ASF's can have the white spotting, that is actually white unless they are fed a very fat diet. It will make their fur extra greasy. A norway rat that has white spotting may not remain a brilliant white, but if it's a tan beige color, then it isnt an albino.
Do you think you have albinos?
An albino will be quite white all over with light pink eyes, and with no dark spots of color anywhere on the body.
A siamese rat which is on the same locus as albinos, (like a siamese cat), will have brown color in the cooler extremities of the body like the tail, feet, ears and most prominently the nose. (and the rump too) It's a gradient of color, and their eyes will be a bit darker than an albino, but still very red color.
I know that may not make a bunch of sense, but it is possible for you to have some abino rats being fed a poor diet giving them a yellowish greasy look.
If not albinos, then it is perfectly natural for them to have a yellow, beige or red color and not be dirty or greasy, it's just gene's at work.