title: Render only specific texture color - OpenGL
body: <p>Let's say I have this texture on a polygon: </p>
  
  <p><img src="https://psychoart21.files.wordpress.com/2011/06/red-blue_stripes.gif" alt="img"></p>
  
  <p>How would I render that polygon and only allow the blue color to shine through and de-saturate the red color?  I assume it will require the use of a specifically designed OpenGL shader. </p>
  
  <p>Are there any good examples of this for specific values i.e. if blue > 200 and red &lt; 20 and green &lt; 20 then render that color else, desaturate the color. Would I be manipulating the color buffer?</p>