three.js modify material ( no uniforms needed )

//https://threejs.org/examples/?q=webgl_instancing_modified#webgl_instancing_modified

const material = new THREE.MeshMatcapMaterial( { color: 0xaaaaff, matcap: texture } );

material.onBeforeCompile = function(shader) {
  shader.vertexShader = shader.vertexShader
    .replace("#include <common>", `
            attribute vec3 instanceColor;
            varying vec3 vInstanceColor;
            #include <common>
          `)
    .replace("#include <begin_vertex>", `
            #include <begin_vertex>
            vInstanceColor = instanceColor;
          `);

  shader.fragmentShader = shader.fragmentShader
    .replace("#include <common>", `
            varying vec3 vInstanceColor;
            #include <common>
          `)
    .replace("vec4 diffuseColor = vec4( diffuse, opacity );", `
            vec4 diffuseColor = vec4( diffuse * vInstanceColor, opacity );
          `);

  //console.log( shader.uniforms );
  //console.log( shader.vertexShader );
  //console.log( shader.fragmentShader );
};