I tend to doubt Peter David made her white -- I don't recall him making any comment on her race in-story in the earlier issues of the run, and he wasn't in charge of the art. Seems like it would be the colourist who is the more likely culprit there.
Peter David did directly address Darwin's skin colour in-story though, with reference to how his powers had resulted in him having a whiter appearance over time. After that he wrote about Darwin reverting back to his more natural skin tone, at which point the art went along with the script (most of the time).