"normal+diffuse mask" decal like this possible in UE4?

jiggywattart

I noticed these normal decals from an Overwatch reference that somehow also allow diffuse information with a mask:

From what I've experimented with, it doesn't seem possible in UE4? I was hoping someone knew if there was an actual solution or if this is just a limitation of the engine:

Currently, it's a waste of polys but I'm just duplicating 2 versions of the decal and layering on top of each other. For some reason the roughness values change but it's the best result I got so far:

Rangaros

Is this what you're looking for? I think from your post this is what you mean to do

Using a mask I lerped it between the decal base color and colored the mask with a color and multiply node. You could make a mask for what sections you want to have a different color and then have it only applied to those area's.

For Overwatch they got rid of their blue channel in their normal maps (at least that's what it seems like because if you rip the textures from Overwatch they are all missing the blue channel color) and rebuilt the blue channel in engine and packed a mask into the blue channel. So if you want to optimize it like Overwatch you could do that too.