Really cool idea!
Makes me remember a Mario Party (I think it's a party game) where you need to select a character's face from a swarm of other faces, and it gets increasingly harder with more subtle variations.
The sound design is well done, I was grooving with that music. Really liked the extra polish of showing the player where the spy was if they failed, although having that interaction take a second more would be clearer for the player. Or maybe have just an outline appear, since after that I couldn't discern what was different about that specific spy.
I did understand somewhat how it fits the theme, although it doesn't seem like the other spies are looking for each other, so I think it kind of misses a bit of the theme fit.
Good variation on differences between spies, and if there were different environments, maybe even having little environments with set dressings could be interesting. Opening doors, moving things out of the way to be able to see the spies in certain zones.
Really liked it!