overlay two materials on top of each other (material with base color + material with texture)


I am relatively new to Unreal Engine and game development in general (except writing code), so my knowledge is basic about everything

Appologize if this is basic stuff, but I was not able to solve this problem with youtube or forum posts.:rolleyes:

In my game I am trying to create, the player can chose a vehicle, and pick a base color for the vehicle with some parts unaffected by the base color.

My problem is, I don’t know how to overlap two textures/materials, so that I can change the “underlying” base color of a mesh and overlay a regular texture over it.
Or in other words, the texture should overlay the base color only where there is something painted in the texture, else the base color is shown.

To get more specific:

I did a model in blender (see below) and painted it with substance painter. On the car, I want to change the color of the blue-ish parts (for example the small box on the roof, the middle part of the fender, the cabin, etc.) of the mesh to lets say red, yellow or whatever color, but I don’t want to loose the dirt and other details I painted on the fender or affect the other parts of the mesh (black edges of the fender, roof, mud flaps, etc.)

I’ve tried using a second UV channel with the parts masked I want to change. But then in Unreal Engine I don’t know how to mask them with the second UV channel and overlay the regular texture I created.

Another approach I tried is using vertex colors. Since I setup vertex colors in blender for substance painter, I saw that Unreal Engine recognizes them.

But again, I don’t know how I could use the vertex colors to somehow setup a mask and use this mask to apply a base color for these parts and then overlay the texutre over it.

Can this be solved in UE, or do I need to go back to blender and setup my model differently?