Default Conditional Formatting Grayed Out in Subform? 2007

Hi, I have a subform in datasheet view and need 4 conditional formats based
on a percentage (every 25% a different color). Thought I would could do this
via Conditional Formatting by setting 3 conditions based on the percentage
value (=.75, dark green; .25, red; = .5 AND .75, light green) and the
remaining percentage (=.25 AND .5) could be yellow with the Default
Formatting. It appears to work in the design view of the subform but in the
actual form it does not. The Default Formatting for yellow never shows when
true and when I open the Conditional Formatting window, the Default
Formatting is actually grayed out. Am I missing something here? Any help
would be great. Thanks in advance.