title: Detecting background color in shader
body: <p>Is it possible (in shader) to change the color of pixels which are identical to the background color?</p>
  
  <p>Thanks</p>
  
  <p>Edit: 
  The background color is white. So is it not possible just to compare each pixel color to white color in Pixel Shader and if equal then just replace it with a desired color?</p>