if the same color is acceptable for each multiple of 5
try
if(A3<"",(mod((year(today())-year(A3)),5)=0)
and set your format

"PAR" wrote:

I would like to have a cell turn a color when the value of the following
formula is a multiple of 5.

Year(today())-Year(b2)

b2 = date of hire

Thank you