You can create a discrete calculated field that will allow you to assign any colors you would like to any range you would like. For example,
IF [Value] > 500 THEN "Green"
ELSEIF [Value] > 400 THEN "Blue"
ELSEIF [Value] > 300 THEN "Red"
Hope this helps,
Most of data that I work with is enrollment data. You can probably see how certain counties or states would have considerably higher enrollment numbers than most.