Outlook Conditional Formatting

Diceicle

I received a query and am wondering if its possible.
A colleague is looking to highlight certain email addresses (in red, in the address bar) when they are composing an email.
The purpose is to stop emailing the wrong person.
Is this possible?
I understand it is possible to highlight emails already in your inbox that have come from certain people but what about highlighting the name prior to it being sent?
Haven't been able to find a solution online as of yet.