Hi Justin -
You can accomplish this by comparing the two fields using text mode code. The easiest way to explain it is to add the fields to the report, then use the Advanced Options to create the condition, i.e., Red when 'greater than' plannedCompletionDate...Of course, you won't be able to pull the field name "plannedCompletionDate" into the advanced options field. So... Save it, then switch to textmode.
There are two things to notice... leftmethod and lefttext lines... You'll notice you only have the rightmethod line item so you need to add the rightext line item and for each replace with =plannedCompletionDate at the end like this...
styledef.case.1.comparison.rightmethod=plannedCompletionDate
styledef.case.1.comparison.righttext=plannedCompletionDate
Here's another article on the community that may help also.
Hope this helps,
Teale