Very nice work.
I have read that using yellow Rit with a little golden brown Rit imparts a nice color to the body of a horn. Two packets of dark brown, with a pinch of black are supposed to give a rich, dark brown color to the neck.
I have also heard, though I haven't tried it, that aqua fortis on the neck gives a nice black. Rubbing the neck with olive oil after the aqua fortis treatment removes the scaley appearance.
The reports I have recieved of using Rit as a horn dye have suggested that Rit is pretty color fast, even with hard use.
J.D.