Yes, once upon a time, "white gas" referred to unleaded gasoline, as well as to stuff like Coleman fuel. That was a long time ago: as Wikipedia says, "when leaded gasoline was the norm.". Coleman fuel is not gasoline, and it will wreck your car's engine if you fill your tank with it. But it does work fine in model engines. The OP asked what Coleman fuel was, not for a list of all the possible meanings of "white gas."