title: Calculating color combination with hex values
body: <p>In additive color mixing primary colors are Red, Green and Blue (RGB).</p>
  
  <pre><code>Red    = #ff0000
  Green  = #00ff00
  Blue   = #0000ff
  </code></pre>
  
  <p>Combining <strong>Red</strong> (<code>#ff0000</code>) and <strong>Green</strong> (<code>#00ff00</code>) makes <strong>Yellow</strong> (<code>#ffff00</code>)</p>
  
  <p>Is there some formula to calulate the hex code of a color resulting from the combination of two others ?</p>
  
  <p>Something like <code>#ff0000 + #00ff00</code> when applied to such a formula gives <code>#ffff00</code></p>