Some users have color printers as default and trying to set b&w as default instead.
Here is a linkto some info on setting default printers from the command line. It is a couple of years old so you will need to do some testing on the OS's in your environment. You could use these commands as the base for a script.
You could also try this link.
Have a look into CUPS. We add all of our printers using this, if you query your printer type with this:
lpoptions -p printer -l
Then it will give you a bunch of options that you can define by script. One of those will probably be setting the colour settings.