Hi Nicky,
1. Yes they would likely have been painted RAF blue,I bought the remains of an RAF Mk6 for parts and that was painted RAF blue from the factory,with a later respray in the same colour.
2. Don't know,but you might be able to get your vehicles record card from the RAF Museum using the chassis number.
3. The Mk6 was basically a civilian vehicle,the only real military specific parts were the lights(though some early models had civvy lights) and the jerry can carrier mounted in the rear tub so otherwise much the same as a basic civvy 88".
4. I have some in service photos but will have to locate them,give me a few days.
5. Depended on the unit,but an RAF roundel on the front wing was usual.
Matt.