In the dark knight intro, the Joker along with his goons rob a bank. In the car however, the joker's goons talk about him being out of the operation and still getting a share even though he isn't doing the dirty work. But, when the camera pans up behind the joker right before he climbs in with them, he very clearly isn't wearing a mask. So, how didn't they know he was the joker? Was he going based on the assumption that they wouldn't know he wore war paint like some of his men were discussing right afterwards?
In the linked clip, the van approaches from behind the unmasked Joker and stops several feet in front of him at 0:17. Within one second of the van stopping, the Joker has his mask on. He's still standing several feet behind and to the side of the van, a rather awkward spot for anyone in the van to be looking at. The Joker simply put his mask on fast enough that no one saw his face.
Even if anyone had noticed the makeup, that alone does not indicate that the person wearing it is the Joker. From the discussion in the van, it's clear that everyone is under the impression that the Joker merely planned the job and is "sitting out" the actual heist - they're already anchored to the idea that the Joker is not present. A glimpse of white face paint isn't sufficient to make the guys in the van think that the Joker has changed the plan without their knowledge.
This answer was written based around the bus driver when leaving the heist, as opposed to the goons driving to the heist, but the same principle applies: there's no reason for them to invariably know or somehow stop what they're doing.
Why would they know it's Joker? If they were all hired indirectly (since the bank goons don't know who hired them) and told to wear a clown mask, seeing one of the guys in clown makeup sounds more like he couldn't find a mask rather than him being the unknown mastermind behind it all. Or maybe he's just being really secure in case his mask gets ripped off.
Secondly, already having rammed through the bank during an active heist, what would you expect the bus driver to do even if he did somehow figure out Joker was their boss? The only course of action is to get on with it.
Thirdly, Joker does have some henchmen, like the mental patient we see halfway through the movie, the ones who pour gasoline on the money, the corrupt cops, ... So it's even possible that the bus driver was a henchman, not a goon to be killed.