Since you're getting a "second" ocellaris, I assume that the first is also an ocellaris. So the "pairing" rules apply, and should be easy.
As to the coloration, fish go through stages in life and change barring and coloration through the stages. Much like my gray hair and wrinkles now that I'm 7 years old versus when I was three (yesterday)
It could be from hosting, but I think it is more of growing up.