Previously I had asked a question about Adobe printing different colours between PC and Mac, but it turns out that my client is experiencing this issue when printing any documents.
I was able to test print two versions of a client's brand-standard RGB value from two machines on the network and they were very different shades of blue. The problem appears to be at the OS (or perhaps driver?) level and not from, say, differing colour profiles within a program since the problem seems somewhat universal across the OS. They also mentioned another employee with a Windows machine as having "the same problem printing."
I've attached a photo showing the print job sent from two sources:
1) a Macbook Pro running OS X 10.11.6 El Capitan 2) a Windows 10 system with current updates installed (as of posting)
These came from a Word doc (to test whether it was an Adobe-specific issue). They were both printing to the same Xerox WorkCentre 7835 over a network. The only other thing I can think to note is that I could not find any sort of colour management settings in the printer driver from the Windows machine. Just basic stuff like print-quality and supply levels.