Hi Pete.
One of the old tricks was to soak bone bobbins in a weak tea solution (no milk) :lol: to give them a antique look. It may work with antler, start with a very weak solution, then make it stronger if you think it is needed. Also the length of time soaking is trial and error, just keep checking.
I believe the same process works on 'Alternative ivory' if you ever fancy using some. Or you can use 'Dylon' dyes to colour some of these pieces.