I think soil type and trace element availability can also affect antler colour, although I don't know about roe specifically.Tannins are found in a great deal of vegetation not only trees, and the repeated application seems to darken the antler over the course of a season. One returning guest shot a very pale trophy buck with me some years ago, before he took it the animal rubbed his antlers on three separate and very bleached fence posts along a fence line. Others go nearly black in the heather. As a percentage of the points toward eg a Gold medal scoring trophy the colour points constitute a maximum potential value of just 3% of the total.
Compare the fallow antler colours in this photo, one being from the rich ground of the English midlands, and the other being from the nutritionally poor ground of North Wales. All the fallow antler in North Wales is almost white.


