ABS aceton treatment, "white out"

When treating ABS with aceton it has some effects:

aceton vapour: works very well. When dry, plastic has same color as before.

aceton spray or put into liquid acetone: when dry, the filemant changs color into "whitening". A black filament has turned grey, other colors like blue or magenta got ugly whitening.
Does anyone knoe where this comes from and how this could be avoid? I suggest some chemical reaction with too much free air O² .

Regards
Stephan

Aceton vapour is like painting and aceton just attacks the surface. Puttting into liquid or wetting is like dissolving and color is taken out and transfered to the aceton, no way to avoid it.