Are the zombies in left 4 dead in left 4 dead 2

No they are not. The common infected in Left 4 Dead are gray and don't have that many features or details to them. But in Left 4 Dead 2 they have more blood and gore on them and they are more colorful than just gray. But if you are talking about the special infected than yes, those same special infected are in Left 4 Dead 2.