I figured out a workable solution.
In the pivot table, I turned on "Show Totals" in the Year column in the Data section. In the Sorting section, I applied a Descending sort order to the Employee row, based on the sum of Incident Count. I then added some conditional formatting to the Incident Count in the Background color expression formula:
if( sum(INCIDENTCOUNT) < 2, Green(),if( sum(INCIDENTCOUNT) < 5 ,Yellow(), if(sum(INCIDENTCOUNT) >=5, Red())))
This resulted in the following pivot table appearance: