As far as I am aware the French F1s are all Camouflaged Light grey/Dark green. Flying out of "Reims" and "Colmar"
The Spanish fly F1s in a light grey scheme.
I do know that two Mirage 2000 were due to depart Marham yesterday.
Some of the French Mirage 2000 do have a light coloured scheme.
So conceivably it may have been one of those.
I can understand if the sighting was brief , it can be deceptive.
If it proves to be a Jaguar, I would be more than keen to know the location where it is based.