I believe he is indeed a tri colored mottled rusty slate. I have the genetics for one to happen. Slater is looking so fine these days with his mottling getting prettier and prettier.... the tri colored mottled varieties get so nice after every molt. His dad is a tri colored mottled slate, so his mom must probably be someone carrying red, like the red bronze Pretty Girl, or maybe Annabelle the burbon red actually laid an egg, but I don't think it was her... Poor Annabelle has had a difficult time with eggs since her surgery several years ago. I think her oviduct was damaged and she does not lay eggs well. Anyhow, I can only guess really on the mother but those are my guesses, that it is the red bronze hen.