Default Printing Randomly Changes to Color Printer

Where did you set the mono option? It must be done in Printer Properties > Advanced tab > Printing Defaults button. If you are printing via a server, this must be done on the server. Many people try to set it in Printing Preferences, which is the wrong place.

Also, if this happens with Word, remember that Word saves some printer settings with the document. I know this happens with paper settings, but I don't know what other settings are affected. I cannot check it now, as the PC I'm at does not have any printers installed, but will do so tonight or tomorrow.

Where did you set the mono option? It must be done in Printer Properties > Advanced tab > Printing Defaults button.

Haven't heard the word Mono before in relation to default printing.

Never heard of Word saving default printer properties and this doesn't make sense to me why other users wouldn't have the same issue. It's only two users out of 15 that this happens to and the same documents circulate between all of them.

Are you saying you have two printers and Windows is randomly switching to the color one when you expect the mono printer to be the default?

If so which are the two printer models?

Mono means "black and white". I'm assuming you want your printers to default to that, but sometimes they don't. However, on re-reading your question, @MASQ's interpretation may be what you're trying to say. Can you clarify that?

And yes, Word does save paper settings (size, type, tray) with the document. I have since checked and colour/mono (B&W) is not saved.

In this scenario one printer / copier is configured twice with the same IP. The reason for this is it saves money not printing to color by accident. Also saves on time.

All the computers have the 'Company Printer (BW)' and the same printer /copier saved as 'Company Printer (COLOR)'.

Configuration:
Connect manually to the printer and name it 'Company Printer (BW)', go into preferences and turn off duplex, color, all the features we like to print in black and white.

Connect to the same printer again using the same IP but this time give it the name 'Company Printer (COLOR)', go into preferences and select color printing, turn off duplex mode, etc.

Very common practice and has always worked well except now for these two computers change the default printer from time to time.

So MASQ's interpretation was correct.

2 things:

1. You talk about (printing?) preferences. As I explained, the settings need to be made from Printing Defaults, not Printing Preferences. Printing Preferences does not change the default.
2. If you did use Printing Defaults, have you checked the registry for old printers, as I suggested in my last comment?

hdhondt, here are the results in the registry

actual printers showing on the computer.

This is confusing. The first 5 printers are connected via a server. The last one is connected directly to the PC, either via USB or via IP. I think you need to sort out which printers you actually want to use: local, or via a server,

Only the Xerox Main Office (BW) printer matches the registry entries. It is possible that removing the others will fix things. If not, you will need to reinstall them. But, first check which printers you actually use: local or network.

And, before doing anything else, please tell me whether your default settings are made in  Printing Defaults or Printing Preferences. That was in my first comment, and it has never been answered.

I removed all the printers and deleted all the registry settings corresponding with them. Reinstalled and they're stable now. Interesting, after doing this they don't show up in the registry. Working better though.

Glad it works! And thanks for the points!