As Apo said the chat is the best source of info of who's shooting what, you just need to put it against what you see in the cockpit.
So if you see a "Red killed Blue" msg and you see the plane going down you'll know he's there.
A good little tip I've used is getting my TGP on them from a distance to make out what markings they have.
It is difficult, firstly to find them and then track them long enough to see any markings but it has worked for me in the past.