Decals in Blender are opaque and occlude the underlying surfaces and materials.
To integrate a decal and so create the illusion of surface detail, a Decal's material can be matched to other materials.
Info Decals cannot be material matched, because they don't imitate surface detail.
Keep in mind
Only Materials with a Principled BSDF shader node at the end can be matched.
Understand, that any nodes connected to the inputs of this shader will be ignored. Keep it to simple parameter based materials, for now.
Decal Materials have up to 3 components, each of which can be matched to another material.
Simple, Subset and Panel Decal materials and their components
Any number of Simple, Subset or Panel Decals.
Info Decals and non-decals among the selection will be ignored.