This is just passing on what others have said int he past. It is a DIR thing. In caves where it is black the light reflects off the mask. the DIR folks would also say,,,, all gear should be black. It probably makes sense in a cave environment. Most if not just many of the rules from DIR have been taken form the caves and promulgated to not only rec divers but all diving conditions. They have another thing they do. One rig set up for all diving. So it may not be needed in rec diving but it may be in cave diving and because of the rule is perhaps inappropriately assigned to rec diving. Just a different set of doing things between tech world and rec world. Kind of like doing a night dive in your pool and having to have 2 lights with you because that is what is done in caves. I would not worry about what your mask is,,,, so long as it works for you in the dive conditions you dive in.