Secret advertisement

I want to take my wife out on a date. Unknowingly, I've been chatting with a guy that wants to get to know her and is also interested in dating her. As he and I get to know each other more, I arrange to have him be at the same location as I take her. Between us guys, she's going to wear something inconspicuous that will serve as an advertisement that I'm serious about her being approached and hit on. A color lipstick, hoop earrings, a specific color or her hair a certain way is what I'm talking about. Nothing too obvious as I don't want her to know anything. I want to see how far she takes things and would encourage her.