this problem:

picture credit to Sauris

I tried messing with the normals, specular, diffuse, whatever the rgb one that create a style uses is called, but couldn't tell what it's from still

Finally! A question I can actually answer! It's a layering issue. What do I mean by that? Hairs are made of strips of mesh layered on top of each other. You want the game to render the bottom layer first, then the layer on top of that next, then the layer on top of that next, and so on until it reaches the top layer. You want the game to render the top layer last of all because that's the layer you'll be looking at. You have to tell the game which layers are the bottom layers and which layer is the top or it gets confused and doesn't know in what order it should display the layers of mesh strips; when this happens, the bottom layers show through the top and you get the issue you're having problems with. I hope I've explained it well.

How to fix this? You have to take the mesh into Blender, Milkshape, or another 3D modeling software--one that can show transparency in the texture--separate the layers, then join them again beginning with the bottom layer and working your way up. Milkshape is a bloody nightmare to work with but people swear by it when it comes to re-ordering layers. A lot of people like 3DS Max because it will show alpha transparency, while supposedly Blender can't, and I'm told that you need the software to display alpha transparency so you can catch problems early on. Others say Blender actually can show alpha transparency but you have to set it up. That's regarding older versions of Blender; I have no idea if Blender 2.8+ can show transparency.

In case you're wondering what I mean by alpha transparency...you know how the hair's texture has an alpha channel and how the channel is painted so that it shows whisps of hair? It's done that way so that the ends of each mesh strip appear wispy and not blunt on the bottom. In Blender, (which is what I'm most familiar with), you'd add a material and import the texture, then set the 3D viewport to texture shading so you can see the texture on the mesh. If you have Blender set up to display alpha transparency then the ends of each mesh strip will look wispy--Blender will show the texture as it's meant to appear in the game. Make sense? Hope so. Here's a tutorial that may help. . It's for Sims 4 and for 3DS Max but it may help you. The concept is the same.

Anyway, the problem has nothing to do with texture and everything to do with the order of the mesh layers the game displays.

Editing to add: After taking another look at the image, it appears that the normals are flipped. I'd have to see the mesh to be sure, however.