Anybody who’s ever used strong neutral density filters knows about colour casts. Whether it’s the B+W 10 Stop or the Lee Big Stopper, they’re just inevitable. Each filter presents a different colour cast. The same filter can also offer a different colour cast on different camera bodies. The typical way to deal with it is to play around with your white balance to try and correct for it.
Without a good reference, though, shifting the white balance to fix it in post can be a bit of a crap shoot. This video from Mike Browne talks through the problem, and shows a couple of different ways to make adjustments to fix colour cast issues. One is by setting your white balance in the camera, the other is by shooting a neutral reference that will let you do it in post.