So I was watching this video pretty closely to make sure I haven't missed any customization options. I do hope that some options are missing from this benchmark because, unless I am missing something, it won't be possible to customize the color of Au Ra horns. Colors appear to be exclusive to each clan and gender. Images of female Xaela (seen
here) appear to have black scales as opposed to dark blue, but that might just be the lighting. It's hard to say, but I didn't see any option to change horn color as they went through each setting in the video.