title: calculate, difference, between, color hexadecimal
body: <p>I would know if somebody knows how to calculate difference between colors hexadecimals?</p>
  
  <p>For a less file, i have this:</p>
  
  <pre><code>@s1-color-main: #2DAEBF;
  
  @s1-color-ts1: #0092b3;
  @s1-color-ts2: #0087a6;
  @s1-color-ts3: #008099;
  @s1-color-ts4: #00758c;
  @s1-color-ts5: #555;
  @s1-color-ts6: #006073;
  @s1-color-ts7: #005566;
  </code></pre>
  
  <p>And i would have something like this for the general case:</p>
  
  <pre><code>@s1-color-main: #2DAEBF;
  
  @s1-color-ts1: @s1-color-main + #111;
  @s1-color-ts2: @s1-color-main + #222;
  @s1-color-ts3: @s1-color-main + #333;
  @s1-color-ts4: @s1-color-main + #444;
  @s1-color-ts5: #555;
  @s1-color-ts6: @s1-color-main + #666;
  @s1-color-ts7: @s1-color-main + #777;
  </code></pre>
  
  <p>I searched on web but i couldn't find any thing :(</p>
  
  <p>But i don't know how calculate each difference between the main color.</p>
  
  <p>Thanks for your help ;)</p>