I really don't think that'll ever happen because there are a lot of mounts already that are just differentiated by what color they come it. It lets SE add "more" mounts without actually making more unique models. There is always the chance that down the line some day they will want to reward an achievement or something with a mount and they can just recycle the Falcon model only making it red this time so it is "new." Allowing players to color them at will would kill their reusable value.