There's a blue one and a black one. The black one has some light dusty rust in it but it'll clean right out and be fine. Neither of them has any serious flaky rust in them, they have been hanging up empty in my lockup for years.
Probably have a petrol cap with no gasket but a bit of leather or old welly works well, and there's no petrol tap but I do have a fitting that screws onto the tank and has a snozzle to put a fuel hose on. You can use a plastic beer brewing tap as an inline one or buy an MZ one. I don't know if anything else fits.