I'm not really sure if this will help answer your question but I know for some hairs there are two different materials in unity that allows you to color them two separate colors. As for making it that way idk how to do that. Cause other hairs may only have one material. I assume it may be a blender thing or - youtube may help you?
I was pretty much asking me that too, I wonder if there's a way to bring the exact model from Unity to Blender (since it's a preset and not a model per se, extracting it just gives the normal model) to edit with precision
@yoyeh42221 I've done that a bunch unfortunately, I'm not sure what it could be I guess it's really just an issue only I'm experiencing, that's such a shame! But I'll make do with it. Thank you anyways