Be smarter when coloring fields using percentages Merged

I'm using a Custom Roadmap report where the bars are colored by percentage completed.  Basically I want the not yet started ones to be red, the less than 50% to be yellow, the over 50% to be blue, and the completed to be green.  Or something like that.  But when you select to color them, it creates distinct colors for all the percentage that current exist at that moment in time.  I can set those and it is fine, but as soon as a percentage change it gets set to a different random color.  I can set it again and eventually I'll get set every possible percentage, but the system should understand that the field is a percentage and let me set colors for ranges even if those values do not currently exist in the data.