I've not used "green" bone right off the hoof but I know that it's been done. It needs to be boiled and bleached to get all the fat and crap out of the bone. Cattle shin bone seems to be what bone suppliers use and some of the best bone comes from South America because it is more dense(I don't know for sure but it may have something to do with growth hormones we use here in the states). Ofcourse, then it has to be D R Y before you use it because bone will move like crazy otherwise.
I have heard of some guys going to PETCO or other pet food suppliers to get bleached bone pieces. I picked up some bone at the local PETCO and found some pieces that would be usable.
Dying can be done using Fiebings Leather Dye. Experiment with the colors to see what you like. Clean the bone surface with acetone and then soak it in the dye for desired effect. The longer you keep it in there the deeper the dye goes...again, experiment. EVERY PIECE of bone you dye will be different. You need to dye multiple pieces at the same time to get pairs that will match up. I know guys that will soak the bone for a month, jig it, warm the bone up with a torch, soak it a little more, etc. till the desired color will be arrived at.
I'm not aware of any sealing that is required for bone. The best treatment for bone to keep it from drying, cracking, and nastyfying in any way is to rub in a small amount of Formby's Lemon Oil Treatment from time to time. Works well on stag too.