three.js/examples/js/shaders/ColorifyShader.js

( function () {

	/**
 * Colorify shader
 */

	const ColorifyShader = {
		uniforms: {
			'tDiffuse': {
				value: null
			},
			'color': {
				value: new THREE.Color( 0xffffff )
			}
		},
		vertexShader:
  /* glsl */
  `

		varying vec2 vUv;

		void main() {

			vUv = uv;
			gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );

		}`,
		fragmentShader:
  /* glsl */
  `

		uniform vec3 color;
		uniform sampler2D tDiffuse;

		varying vec2 vUv;

		void main() {

			vec4 texel = texture2D( tDiffuse, vUv );

			vec3 luma = vec3( 0.299, 0.587, 0.114 );
			float v = dot( texel.xyz, luma );

			gl_FragColor = vec4( v * color, texel.w );

		}`
	};

	THREE.ColorifyShader = ColorifyShader;

} )();