(This is, among other things, an excuse to post some aviation pr0n).
Exhibit A - A Sopwith Camel:
Spot those rather attractive roundels on the wings and the fuselage?
Exhibit B - A Supermarine Spitfire:
Handsome isn't it? The roundels help too...
Fast forwarding a bit, the Handley-Page Victor. And what a dapper, if somewhat unsung, beast that is:
The English Electric Lightning:
Pretty clear which Air Force those chaps are flying for, wouldn't you agree?
(I'm nearly at the point. Bear with me)
Not such an easy tell, eh?
And finally the (new) Typhoon:
Looks more like they are representing Jacob's crackers, don't they?
Now I appreciate that identification of friend from foe is more likely to be done with means other than the naked eye, but I still think it is all rather sad.