I'd like to add this probably has no meaning, but I saw somebody say how on the antlers of Xerneus it has red, blue and yellow.
I highly doubt this, but Yveltal is red, Xerneus is blue and maybe Z???? is yellow?
I definitely think for sure it will be yellow or green. It's hard to figure out where Game Freak is going because I don't know where exactly is this "DNA" stuff is playing a role. Maybe the three legendary are related DNA wise?