1996 Toyota Camry blue smoke

My car is blowing blue smoke only when I first start it up. Once I've travelled for a little, the tailpipe blows clear. This is worse when the engine's cold, but also happens when I start up after driving. The performance has not changed and when I lift the lid and listen to the engine while running, it sounds smooth - no missing. Oil level stays good and there is no evidence of a leak under the hood or on the ground below the car. Can't afford even a diagnosis right now, but I'm afraid to keep driving it without doing anything. Any ideas? Thanks.

Ann