That Lightning looks fantastic, even if it is wearing a pretend livery. (Took me a while of guessing to work out which mark it was, and when I looked it up I was wrong anyway!).
And yes, I agree, they've done well to keep the exhibits in such good condition. Right now, it's probably the Varsity and Meteor that need a little work. The Varsity just needs a lick of paint and a clean, more than anything, but the Meteor is currently lacking it's right wing and the rudder (and I'm led to believe they're fairly important parts of the aircraft! )
Here goes.. she's a Lightning F.53, 53-693 (ZF588), ex RSAF. She doesn't wear Saudi colours because of a political reason.. I think. I'm not clued up on why but I am on that particular Lightning.
It's for the same reason you'll never see a Saudi-painted aircraft anywhere outside of Saudi Arabia unless it's just passing through. Their rules are very strict on this. Once a plane is no longer owned by the Saudi government or a Saudi business, it must have all evidence of it being a Saudi-based aircraft removed (registration, national insignia, flags, etc). Some of it is due to the nature of their flag and its resulting issue with Islamic Law (the flag has one of the "Pillars of Faith" on it) and some of it is simply Saudi Arabia's registration system in where the registration is owned by the operator and that if the owner is not in control of the aircraft, then the registration must be removed. If the aircraft is no longer registered in the kingdom, then it is also no longer a Saudi aircraft and thus cannot carry the Saudi flag or roundels.