Hello,
sorry because I am new to this amazing product but I am having issues about the colors of hair and beard in my characters. They show pinkish, green reflections as in the pictures. Do you have any suggestion how to fix this? Thanks!

Did you ever try to delete the hair, and then reapply the hair?
Save all the hair textures and then apply them again to the hair base.
I don't think I have ever had that problem. Did you try and use the hair on another character?
Those are some suggestions you can do.