tell the difference between which?
the commonly called black and white perc is actually an ocellaris variant and is all black and white, sometimes with an orange or brown mouth when younger or brown and white when very young - but in general ocellaris develop there color much faster than perculas...
and onyx percula has orange face, orange tail and everything else is mostly black and white... there are some minor variations in what people consider onyx, but a black dorsal is pretty much my standard along with the black connecting the 3 white bars...