title: Check pixel color and trigger a bash script
body: <p>How can we check the color of a determined pixel(x,y) and, if it is equal to a certain value, run a bash script.</p>
  
  <p>In particular I'd like to write a script that:</p>
  
  <ol>
  <li>Wait for a determined key being pressed (in particular 'j' or 'f' or 'space' or 'y').</li>
  <li>Compare the color of 4 pixels to a color. If we found that one or
  more (if there are more we can pick the first or a random one) we
  can go to step 2.</li>
  <li>Run a bash script.</li>
  <li>Go to step 1.</li>
  </ol>
  
  <p>I know only how to complete step 3, the first 2 steps are out of my coding skill.
  Can you help me?</p>