I disagree Mr V, the red droid (formally known as R2D2) veers to the left and the new head is following the track of R2 in the next shot.
I really do think that the confusion is caused by over familiarity with the original (flawed) material.
I've tried this out on someone not that familiar with the original footage and they instantly identified the blue droid at the front as R2 and not noticed the red one until it was pointed out and the change explained.
The R2 unit colour variations like the one used here is more a PT thing which might add to the sensation of "something is wrong with picture".
There is a R2 unit right at the beginning of the Mos Eisley sequence that has a white dome with white panels and a green frame thing for the eye (please excuse the crudity of this mock-up) :
If a colour scheme like that were used it would make the droid look even less like R2 and push the impression even further away.
++UPDATE++
I posted the above before I saw the alternate view and which shows the original droid was never Artoo in the first place.