You could try some Knoblauch Antler Stain, it comes in a brown or reddish/ brown colour. If the antlers are rough you may want to lightly sand prior to appling the Antler Stain, just so the get a more realistic finish. Taxidermist reccomended it after we attempted to paint some elk found up north for our hunting camp and said it does a nice job vs painting.
Antler Stain
Good Luck