three.js/examples/js/shaders/TechnicolorShader.js

( function () {

	/**
 * Technicolor Shader
 * Simulates the look of the two-strip technicolor process popular in early 20th century films.
 * More historical info here: http://www.widescreenmuseum.com/oldcolor/technicolor1.htm
 * Demo here: http://charliehoey.com/technicolor_shader/shader_test.html
 */

	const TechnicolorShader = {
		uniforms: {
			'tDiffuse': {
				value: null
			}
		},
		vertexShader: /* glsl */`

		varying vec2 vUv;

		void main() {

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

		}`,
		fragmentShader: /* glsl */`

		uniform sampler2D tDiffuse;
		varying vec2 vUv;

		void main() {

			vec4 tex = texture2D( tDiffuse, vec2( vUv.x, vUv.y ) );
			vec4 newTex = vec4(tex.r, (tex.g + tex.b) * .5, (tex.g + tex.b) * .5, 1.0);

			gl_FragColor = newTex;

		}`
	};

	THREE.TechnicolorShader = TechnicolorShader;

} )();