Behavior sounds very roo-like. Novice experience here but by 18 weeks I would think you should have some evident saddle feather coming in if it's a roo? Can you see them on Colonel yet? If you don't see any, lift up the feathers in the saddle area to see if there are any peeking through near the skin. We could do this with our Orpington at 8 weeks.
I can't say enough good things about them.
He is an 18 week old Speckled Sussex. Very calm, but the only one who doesn't seem to like to be touched. I live in Hardinsbrg, Ky if anyone close by with a good place for him would be interested. I'm very sad to lose him, but we only have a small flock of 6, so 2 roosters is too much chance one will get hurt.