I have several European deer heads that the horns are noticeably starting to fade. Is there anything you can put on them to keep them from fading that won’t change the look of them or make the horns shiny?

Are they fading into antlers?

Pick a Minwax wood stain that mimics the color of the horns when they were fresh and stain them. I have also heard that old English furniture polish does a good job.

Old English in the dark color.

Brown shoe polish works well. Liquid if you can still find it paste if not. Go as dark as you want.

Minwax Poly (wipe on)

It'll give a little shine and protect from fading

The small deer on the left is his natural color (he had pretty dark antlers), although he has faded a bit. The big guy on the right was found dead and the antlers had sun faded to almost white. I used Miniwax Early American stain that I diluted (maybe 50-50) with paint thinner. It might be a little darker than some would like, but looks pretty good.