Spent the last damn hour scouring around and have managed to find the exact colour code for a burgundy R33 Skyline as AN0.
Any Skyline's colour can be sourced from the original engine plate using info from this link:
http://www.courtesyparts.com/paint/touchup_howto.html
Anyway, now just trying to find someone outside of Japan with AN0.
It seems as though everyone (...well in Aust., that is...!) only has AL0 (Ruby Pearl). It looks close, but I don't think it's exactly the same.
Anyway, just thought someone else might find this useful.