title: Eliminate a color channel when rendering an object in OpenGL
body: <p>Am wondering how to eliminate the red channel when rendering some objects in OpenGL.</p>
  
  <p>I can do this easily using a fragment shader but unfortunately I can't use shaders for this particular project.</p>
  
  <pre><code>Disable the red channel
  DrawOject();
  Enable the red channel
  </code></pre>
  
  <p>Is there any solution for this? </p>