That isn't possible in the Hud configuration but can be done by adding color conditions to the stat itself if you want (registered versions only - this isn't possible in the trial).
To do that go to Configure > Stats and select the appropriate cash or tournament section, then "Players" and "Stats".
Find your stat and look at the Definitions tab to identify the 'opportunities' column for the stat. Make a note of this name.
For "CBet Flop" that is "cnt_f_cbet_opp" as shown below - most normal percentage stats work like this.
- 2012-08-22_09h05_22.png (18.37 KiB) Viewed 1479 times
Click the Colors tab and enter a color expression as shown below. Replace "5" with the number of opportunities you require. Replace "50" and "70" with whatever value range you want, and pick a color. Be sure to tick the 'Hud' checkbox to have your colors apply to the Hud. (Tick 'Tracker' if you want the colors to apply to reports as well.)
Click 'Save' to store your color condition, and click 'New' if you want to add another color.
The first Color Condition to be true is applied, so think about what order you want to add them if you want to use a mixture of different conditions.