A basic vertex/fragment shader combination showing colours

From The WebGL Cookbook

Here's the vertex shader:

attribute vec3 aVertexPosition;
  attribute vec4 aVertexColor;
 
  uniform mat4 uMVMatrix;
  uniform mat4 uPMatrix;
 
  varying vec4 vColor;
 
  void main(void) {
    gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
    vColor = aVertexColor;
  }

...and the fragment shader:

varying vec4 vColor;
 
  void main(void) {
    gl_FragColor = vColor;
  }