It looks like Platy is a combo of two different mutations of the same gene (alleles). So in that respect platy would be the same as a BEL, just not a totally white one. One of the mutations is lesser and the other has been called "hidden" because they apparently look normal.

So platy X lesser would produce eggs each with a 25% chance of being BEL's, 25% chance of being platy, 25% chance of lesser, and 25% chance hidden. The BEL's would be the same as a lesser X lesser breeding.