There is reasonable room to speculate that some of the dyes have more function than a simple pallete shift. The description for the Abyssal dye, as an example, states "as though it were drinking in the very light that touches it," maybe hinting at some sort of extended animation or perhaps a different shader to the applied armor in question. This is just speculation, however, and remains to be seen in-the final game, however but it is backed up by some of the official Blizzard statements on the dyeslooking unlikely.