How to change the color of face from a obj file

Load a obj file

            const loader = new OBJLoader(manager);
            
            loader.load('models/obj/building/111.obj', function (obj) {
                let i = 0;
                obj.traverse(function (child) {
                   
                    if (child.isMesh) {
                        child.name = 'building' + i.toString()
                        child.material = mat1
                       // child.castShadow = true;
                        //child.receiveShadow = true;
                        i = i + 1;
                        buildings.push(child)
                    }

                });

                scene.add(obj);

            }, onProgress, onError);

        function onPointerMove(event) {
						
            pointer.x = (event.clientX / renderer.domElement.clientWidth) * 2 - 1;
            pointer.y = - (event.clientY / renderer.domElement.clientHeight) * 2 + 1;
            raycaster.setFromCamera(pointer, camera);
            
            let intersects = raycaster.intersectObjects(buildings);
         
                        
            if (intersects.length > 0) {


               intersects[0].face.color.setHex(0x1111)
               //I got face,but the face has no color attribute. i want to change color of this face,how?
                
            }

        }

I only want to change the color of face,not mesh. how? thanks.

Unfortunately, this code is outdated. Try it with the approach discussed in: How do I change a IcosahedronGeometry object's face with a click? - #2 by Mugen87

thanks very much! it works!