title: How vim resolve color names in 256-color term?
body: <p>For example,</p>
  
  <pre><code>ctermfg=DarkBlue
  </code></pre>
  
  <p>How vim decides the rgb value for the color name <code>DarkBlue</code>? It was said that it was described in <code>$VIMRUNTIME/rgb.txt</code>. But in some release of vim this file does not exist.</p>
  
  <p>BTW, how vim decides the rgb value for a numeric color, such as</p>
  
  <pre><code>ctermfg=0
  </code></pre>