It also means coolant in the combustion chamber. Check your rad for oil floating on the coolant, do a rad pressure leakdown test or do a cylinder compression test and possibly find a head gasket failure.
Blue smoke would be oil. I believe some 240s had a oil vapour vent that fed back into the intake. Worn engines have higher pressure in the crankcase and that would put more oil smoke into that area. Lack of oil changes could eventually wear out an engine too, possibly even a Volvo, and would also make (light) blue smoke out the tailpipe.