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

( function () {

	/**
 * Colorify shader
 */

	var ColorifyShader = {
		uniforms: {
			'tDiffuse': {
				value: null
			},
			'color': {
				value: new THREE.Color( 0xffffff )
			}
		},
		vertexShader: [ 'varying vec2 vUv;', 'void main() {', '	vUv = uv;', '	gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );', '}' ].join( '\n' ),
		fragmentShader: [ '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 );', '}' ].join( '\n' )
	};

	THREE.ColorifyShader = ColorifyShader;

} )();