JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdn.rawgit.com/mrdoob/three.js/master/build/three.min.js"></script>

CSS

body {
	  margin: 0;
}

JavaScript

let camera, scene, renderer, material;

let t = 0, colorHSL = {};

const geometry = new THREE.PlaneGeometry();

var init = function(){

    camera = new THREE.PerspectiveCamera( 70, window.innerWidth / window.innerHeight, 0.01, 10 );
    camera.position.z = 1;

    scene = new THREE.Scene();


    material = new THREE.MeshBasicMaterial( { color: 0x00ff00, vertexColors: THREE.FaceColors } );
		material.color.getHSL( colorHSL ); // save current color value as HSL

    const mesh = new THREE.Mesh( geometry, material );
    scene.add( mesh );

    renderer = new THREE.WebGLRenderer( { antialias: true } );
		renderer.setPixelRatio( window.devicePixelRatio );
    renderer.setSize( window.innerWidth, window.innerHeight );
    document.body.appendChild( renderer.domElement );

}



 var animate = function() {

    requestAnimationFrame( animate );
console.log(scene.children)
    
    t += 0.01;
    
    const l = Math.abs( Math.cos( t ) ); // only animate lightness between [0,1]

  scene.children[0].geometry.faces[0].color.setHSL( colorHSL.h, colorHSL.s, l );
  //geometry.colorsNeedUpdate = true
   //material.color.setHSL( colorHSL.h, colorHSL.s, l );
    
    renderer.render( scene, camera );

}

init();
animate();