There is no black percula. There is an onyx percula, but it is not all black. All fish labelled as black percula are black ocellaris. All black ocellaris start out with a brown face.
http://img.photobucket.com/albums/v2...d/fish1031.jpg
http://img.photobucket.com/albums/v2...lid/6mnths.jpg
http://img.photobucket.com/albums/v237/sicklid/012.jpg