I'm working on having a column that shows the % of the actual cost to the planned cost and have anything over 80% highlighted. I have the text below, but it's highlighting all values.
displayname=% of Planned Cost
It's not possible to set conditional formatting on a value expression built in a report view. These calculations are carried out in the report only and as such there is no value in the workfront database to compare against for conditional formatting.
The way to achieve this would be to have a calculated custom field on the object you are reporting on, that calculates the % of planned cost. You can then build conditional formatting against this custom field as desired.