Finding the first appearance of the latest item

This proposal employs two helper columns (F:G) which may be moved and or hidden for aesthetic purposes.
Column F is populated using: =IF(OR(A2=A1,A2=""),"",AGGREGATE(15,6,C$2:C$50/(A$2:A$50=A2)/(B$2:B$50=B2),1))
Column G is populated using: =IF(F2="","",AGGREGATE(15,6,ROW(A$2:A$50)/(A$2:A$50=A2)/(B$2:B$50=B2)/(C$2:C$50=F2),1))
The conditional formatting rule is: =COUNTIFS($G$2:$G$50,ROW())>0
Let us know if you have any questions.