Love the idea of Red being jealous of Alan LOL. (Would Alan be jelly too?)
I think Alan would have the time of his life provoking Red, to be honest. Always making double entendres about Liz, referencing their shared past and generally going out of his way to make everything sound extra lascivious and dirty, constantly shooting Red ‘you know what I mean wink wink’ glances behind Liz’s back while touching her elbow or leaning in a bit too close.
And anytime he’d get too close to getting shot, he’d hide behind Liz and tattle on Red. Liz usually just heaves an exasperated sigh and tells them to ‘play nice, boys’