Changing the color of the polygons

I use AR.JS to view models. Is it possible to somehow recolor individual polygons of a model? I can change the color of the entire model at once, but I’m only interested in individual polygons. I have access to the object’s BufferGeometry (see screenshot from the debugger), but I only see an array of points here and nothing about polygons.

I apologize in advance if I described something incorrectly, I’m just a beginner and I don’t understand much yet.

Could you describe what’s the final effect you’re aiming for? May be easier to suggest a way to achieve it.

In most cases, especially when models have non-trivial geometry - the most practical way of changing color is applying it via texture (if the model is properly UV-unwrapped you can easily apply color to only specific parts of it using textures.)

Okay, now I’ll try to explain. As you can see in the screenshot, I have two bones. I want to see which polygons they touch each other. Simply put, you need to find the contact patch of the two models. To do this, I want them to change the color of the corresponding polygons when they intersect. How do I handle intersections - this is most likely not a question for this forum, for a start I just want to learn how to change the color of individual model polygons.