Method 1
The following supplies will be needed: a paper cup, a stirring stick, some latex/nitrile gloves, paper towels, paint thinner, paint brush, small tubes of black, burnt umber and burnt sienna oil paint, spray can of Krylon 1311 matte finish.

Do this in a well ventilated area. Fill the paper cup about ½ full of thinner (in most cases this will probably be more than necessary but you want to be able to do the whole antler/rack with the same mixture for color consistency). Add small, but equal amounts of the black and burnt umber oil paints to the thinner and mix well. You'll have to guess on the amount of oil paint to add - start out with a little then add more if necessary. It will be dark in the cup but this will give a nice antler color when finished. If you want the antler to be a little more brown add more burnt umber to the mixture. If you want the antler to have more of a reddish brown color add some burnt sienna to the mixture.
Put on the gloves. Fold the paper towel up and dip it in the thinner and paint mixture. You could also use a paint brush. Wipe the thinner/oil paint mixture all over the antler. It should go on kind of dark. Then take a clean paper towel and start wiping/rubbing the excess off until you get the look you want. Rub the tips a bit harder to make them lighter in color. Let it dry overnight. If you still want it darker do the same process again in a day or two.
After it looks the way you want and it is dry, seal it with Krylon 1311 matte finish.
Method 2
If the antler doesn’t look the way you want (the antler might not be porous enough and won’t accept the color real well) one other way to do it is to paint the entire antler with a thin coat of white latex house paint. Make sure the coat covers the antler but is not so thick that the paint starts to run. Let the paint dry for a few hours. After the latex paint dries, do the same procedure as outlined above with the thinner/oil paint mixture.
Here is a set of cheaper reproduction antlers I colored. I bought the rack uncolored. I painted it with the white latex paint, then colored with the thinner/oil paint mixture.

