title: how to set colorbox for positive and negative values in gnuplot
body: <p>I would like to set palette rgbformulae in such  way that, the colors will be distributed in positive and negative values equally. I want to go from blue (negative values) to 0 (white), to red (positive values). I can't able to change the rgbformulae for that.</p>
  
  <pre><code> set cbrange [-5:5]
   set palette maxcolors 10
   set palette rgbformulae ? ? ?
  </code></pre>