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

var camera, scene, renderer, renderTarget;
var geometry, material, mesh;

var read = new Uint8Array( 1 * 1 * 4 );
var mouse = new THREE.Vector2();

var windowHalfX = window.innerWidth / 2;
var windowHalfY = window.innerHeight / 2;

init();
animate();

function init() {

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

    scene = new THREE.Scene();

    geometry = new THREE.BoxGeometry( 0.2, 0.2, 0.2 );
    material = new THREE.MeshNormalMaterial();

    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 );
    
    renderTarget = new THREE.WebGLRenderTarget( window.innerWidth, window.innerHeight );
    
    renderer.domElement.addEventListener( 'mousemove', onMouseMove );

}

function onMouseMove( event ) {
		mouse.x = event.clientX;
		mouse.y = event.clientY;
}

function animate() {

    requestAnimationFrame( animate );
    
		camera.setViewOffset( renderer.domElement.width, renderer.domElement.height, mouse.x * window.devicePixelRatio | 0, mouse.y * window.devicePixelRatio | 0, 1, 1 );
		renderer.setRenderTarget( renderTarget );
    renderer.render( scene, camera );
    
    renderer.setRenderTarget( null );
    camera.clearViewOffset();
    renderer.render( scene, camera );
    
    renderer.readRenderTargetPixels( renderTarget, 0, 0, 1, 1, read );
    
		console.log('r:' + read[0] + ' g:' + read[1] + ' b:' + read[2]);

}