they have clear bellies whereas most Normals do not. to be clear: my provided scenario is if one were to mix confirmed Mahogany's and Normals and w/o seeing their bellies or from a confirmed Mahogany clutch. DO NOT pick out random BP's from any clutch and claim that a Normal looking BP w/ a clear belly is a Mahogany. genetics are still very important, not random patterns.
the best way to get a Mahogany is to obtain one from a trusted breeder.