Odd, if downed in July of '44, wouldn't it still have had full invasion stripes, above and below the insignia star? Seems like there should be a white or black stripe above the star, but I see olive drab...
I've seen MTO P-40's using the red surround insignia well into 1944. Are there any other reference photos of this plane or it's squadron mates from the same period that can provide context clues?
I've seen evidence that would suggest the red surround was painted over with blue, and survived many, many years only to become visible after the blue had faded away. This was in a crash sight photo similar to the one V posted, except it was a US naval aircraft discovered in some tropical jungle. That being said, keeping the red surround in the ETO, or even the MTO, wouldn't have the same potential for adverse consequences as it might in the PTO.
I think GQ-U is your smoking gun. The red "L" on the flap is lighter than the OD green and the insignia border is darker. I'd go with dark blue.