title: Calculate new RGB by saturation
body: <p>I've searched Google with no avail.</p>
  <p>If I have the following color <code>rgb(50,100,200)</code>. I can calculate the HSV saturation with: <code>(200-50)/200</code>, which is <code>0.75</code>. If the want the color shade with a different saturation, how can I calculate that?</p>
  <p>I'm using a color picker to get these test data:</p>
  <pre><code>saturation 1.00 = r:0   g:66    b:200
  
  saturation 0.75 = r:50  g:100   b:200
  
  saturation 0.50 = r:100 g:134   b:200
  
  saturation 0.25 = r:150 g:167   b:200
  </code></pre>
  <p>I've noticed with saturation changing, the <strong>max value</strong> (blue channel) doesn't change. <br>
  There is no found ratio between the R-G-B numbers.</p>
  <p>Can I calculate a new shade of color using RGB and not convert it first to HSV color?</p>