Just tested it out. It works. Most likely human error.
Wasn't human error, it was a bug. When I was trying the dyes, I had the fertility crest and the lasting pregnancy from the Broodmother. When the pregnancy was still active, all four mushroom brews would only turn my hair white. When the pregnancy was cleared, I was able to get the hair colored correctly while using the exact same solution I was using. It seems to be some bug in relation to the character being pregnant
I’ve wasted a good 30 minutes reviewing the code. I tried to recreate it organically - something I don’t even do for properly documented reports. I found nothing and I was very bitter about it. You can choose to believe it’s a bug, but there’s nothing for me to fix.
If you’re serious about it and can explain how you consistently recreate this issue, I’ll do another pass. But I promise you pregnancy has absolutely nothing to do with it.