thank you sounds too much work for a different haircolor for me hahahWas a while I did it, but I took the overworld and HD files and just coloured the hair into the desired colour, after that I changed it to a hairstyle that I thought were rarely used.
Think they are in a_2_1_5 and a_1_8_9 for Ultra sun and moon. Tricky part is getting the texture back into the game, unless something has changed in recent time. Did all my editing with some converter tools and HxD editing.
Hope it helps! o/