I dont really have white ones but I do have a color morph from a rock of zoos I have that are almost white centers, with the outer edge being very dark grey to almost black.
There not bleached or anything, not even sure why they morphed. But from the same colony of zoos I have orange center, green center, white centers, orange with some green, with diffrent outlines on them from green to orange, ect...
Maybe some one else will chime in and explain in better, I just know that they are out there. Hope that answers your question.