The photo is an excellent example of just how much variation in markings existed and how different aircraft looked, even down to, as is the case here, individual squadron level.
Next time somebody says "all aircraft of 123FG" or "from 31/2/43 the markings changed from type A to type B" just produce this picture.
Also worth noting is that 2 of the Mustangs have had their fusalage insignia "dulled down" as well.
Great photo.
Nige
http://56thfightergroup.co.uk/