Hi Eric,
First of all, the top image is overexposed. ISO was 640, with f 8 and 1/40. Shot at the same general time as the 2nd one, ISO 200, f 2.8, 1/100. Although your aperture was wider on the 2nd shot (which is very nicely exposed), there are much lower ISO and shutter speeds compared to the top one.
But you're right, there does seem to be a yellowish cast to both of them. It could very well be the optics. How old is this new "old" lens? I have seen old lenses get so yellow (can happen in 15 years or more) that they actually look off through the viewfinder.
The other possibility is that your cam has been switched to a manual or pre-set White Balance function. If it is set to correct for a different color temperature, it will give a different hue. However, this hue will change as your move to different types of light. I'd be willing to bet it's the old glass.