It’s more realistic for it to take a few seconds until you recognise a teammate. It requires you to know just what your teammates are doing and where they are.
Don’t they appear in the map as a teammate anyway? So check the compass and the map and if they’re a friendly, don’t shoot.
Maybe if the Covops has made a radio communication, say from G4, then if you target him in G4 then the red circle comes up instantly, because knowing his location(via the voice chat) makes it easier to tell that he’s a friendly. However, when he leaves the grid, he’ll have to make another communication. Probably best if there’s a new voice chat for this purpose…or maybe ‘hold your fire’ will do