I got to print some this weekend and finally figured out how to do the test properly to get you a good answer.
Contact printing. It takes most of the variables out of the question. (Read, even if I made an error in exposure or color correction those errors are all held in common by every frame.)
I printed all your negatives at once at 3 different enlarger exposures.
I've scanned the print with the middle exposure, it's attached.
I checked several points in PS to measure the color shift and across the board the only thing that changes is the brightness.
For example the pavement/concrete appears purplish but that color cast is essentially the same in each corresponding frame. 3 guys on the bench, left man's lifted shoe measures 31/32/76 in frame 14, 84/87/140 in frame 15, 170,175,230 in frame 16.
Given these numbers, and that the subject probably moved, that there is no way for me to measure the exact same spot in each frame, and that you moved the camera a little I think it's fair to assume that there is no color shift based on the exposure.
Given what I see here I think what you are seeing as a change of color balance is actually a difference in brightness or a difference in the processing your lab did.
Mark Barendt, Ignacio, CO
"We do not see things the way they are. We see things the way we are." Anaïs Nin