How to stencil a image onto a model without it being affected by a Material?

[Switchiro]

I am a relative novice at blender. I am trying to make a cell-shaded character as practice. The goal of this practice is to actually finish a model that I started work on since I usually quit at the Texture/Shading stage of modelling. As such, I made the model in a rush with bad topology.

I want to add eyes and a mouth to the model using stencils.

But when I try to add my stencils on top of my cell-shaded material in the Shading Node Editor, it is mixed with the colour that am using for my material.

How do I stop these colours from mixing?

I made this material by following this tutorial: here

I have looked for tutorials on using stencils but they all seem to use the default Principled BSDF material instead of anything like mine.

I’m using Blender 4.0.

TLDR: How to add stencils on existing materials without the colours mixing?

[Okidoki]

Welcome …

the are often called decals… and you might have a look the docu about projection modifier
or at the following video (or something similar…):

Adding Decals to 3D Models - Blender 2.8 Tutorial

[Switchiro]

Yes, that helped. I managed to put some eyes onto the model. The model still looks somewhat rough but I’ll learn from my mistakes when I start my next model.