Naptha is actually one of the low-octane components of gasoline. That's why you generally don't want to use naphtha/lighter fluid/coleman stove fuel (which are all naptha based) in your vehicle, as it will lower the octane and potentially cause detonation. IIRC, fuel for camp stoves is around 50 RON (the octane scale), whereas gasoline for automobiles is typical in the 80's+.

With that said, there are other differences between the products, that can effect interchangeability. I'm not a chemist, so I can't tell you which are safe to use. The question that I answered was simply, where would one find a source of naphtha?

IIRC, Blast works as a chemist in the petro-chemical industry. He would probably be able to confirm whether or not one could safely use painter's naphtha in a liquid fuel camp stove.