Smoke from exhaust

What is your question?

It doesn't smoke when I first start it... I can drive for about 10 to 15 min then puff of grayish smoke and a slight blue tint comes out then it stops and want do it again till I leave and drive again but the blue tint is gone and it grayish what are the possible cause the car doesn't over heat are anything doesn't use excess coolant could it be a egr valve... Or exhaust manifold gasket ... Or valve cover gaskt