Using Business Intelligence Dashboard Designer : Creating a New Dashboard : Working with Dial Charts : Changing Dial Sector Colors
  

Changing Dial Sector Colors

You can change the color of a dial sector by clicking the small down arrow in the color boxes associated with Range. Select a color from the palette so that you can preview it on your dial chart. Click Apply to preview your dial chart. Click Ok to place your dial chart into the dashboard.
http://infocenter.pentaho.com/help/topic/puc_user_guide/images/18_color_picker.png