I was trying, but can someone help me ?

We have tab 1 where all vacations are mentioned.

We have tab 2 as task list.

The goal is, when planning a task within tab 2 and select a “due date” or revised due date on the day when the person who is assigned to the task is on vacation, to highlight the cell “due date” or revised due date with colour (via conditional formatting.

I tried index match, x lookup but I am did not find a way how to make it working fully :-/. Can someone support and put some idea ?

https://docs.google.com/spreadsheets/d/1z9goAZxzAnH0eH0f-d63m8Ziiu1RM6lnHByCNNZi9K4/edit?gid=0#gid=0

xlookup, vlookup, index and match …