JSFiddle - React, Tailwind, and code Playground

HTML

<script id="vertexShader" type="x-shader/x-vertex">
			varying vec2 vUv;
			void main()	{
				vUv = uv;
				gl_Position = vec4( position, 1.0 );
			}
</script>

<script id="fragmentShader" type="x-shader/x-fragment">
			varying vec2 vUv;
      uniform vec3 colors[ 2 ];

			void main()	{

      	vec3 color;
        
				if ( vUv.x > 0.5 ) color = colors[ 0 ];
        else color = colors[ 1 ];

        gl_FragColor = vec4( color, 1.0 );

			}
</script>

CSS

body {
	  margin: 0;
}
canvas {
	display: block;
}

JavaScript

import * as THREE from 'https://cdn.jsdelivr.net/npm/three@0.115/build/three.module.js';

var camera, scene, renderer;

init();
animate();

function init() {

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

    scene = new THREE.Scene();

    var geometry = new THREE.PlaneGeometry( 0.5, 0.5 );
    
    var material = new THREE.ShaderMaterial( {
    	uniforms: {
      	colors: {
        	value: [ new THREE.Color( 0xff0000 ), new THREE.Color( 0x00ff00 ) ]
        }
      },
      vertexShader: document.getElementById( 'vertexShader' ).textContent,
      fragmentShader: document.getElementById( 'fragmentShader' ).textContent
  	} );

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

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

}

function animate() {

    requestAnimationFrame( animate );
    renderer.render( scene, camera );

}