I have a Dell all in one 968 printer. It recently ran out of colour ink and switche to black and white only printing, It now has a new colour cartridge and can print the test page correctly from either PC or printer control. In Windows (Vista) it can only print in black and white still. How do I tell Windows it now has the colour cartridge?

Hello yes this is possible. When you go to print go to options and then there should be an option to choose black and white only.

If the printer can copy a document under the glass, black and white and color, then it will be a driver issue.
Make and model of your computer and operating system? 32-bit or 64-bit? Was the operating system recently installed/reinstalled/upgraded?
What virus program and firewall are you using?
https://www.instantprintersupport.com/dell-printer-support

It could be the print setting on your computer.
If you're using Windows, with your document open, go to File > Properties/Preferences. In the Print Setup tab, make sure to select "Print using all available ink" in the Ink Use section.
On Mac you can select Color in Print Setting in any expanded print dialog.

I replaced the ink cartridges even though the levels still said they were half full. It worked perfectly.

Please check if your Colour Ink Cartridge is not emply. If their's ink in the cartridge then try to service your printer through the Print Preferences. Your Colour Cartridge Nozzels could have been blocked thats why your printer is unable to print in Colour.

In case if both the above doesn't work then check in the Print Preferences that you should not have saved the option of PRINT DOCUMENT IN BLACK ONLY. hope this helps , AJ

No you need functioning colour cart for black to work.

if the test pages come out OK then the problem can not be the printer !!!!!!!
it must be from the application

One of the possible reason why you can't print black in white because Epson ink jet printers require all of the ink cartridges to have ink in them in order to print any color, black and white, or grayscale images. More than that Epson printers contain a permanent print head that needs to be charged with all colors to work. Even when users are printing black text only, a small amount of color ink is used to keep the print head charged for color printing and prevent air bubbles from entering the color print nozzles which can damage the print head.

I had the same problem. Had no choice but to buy the colors I ran out to make the printer work. In order to avoid future problems and save on color inked I attempted to follow the steps of a previous posting, however, that did not work for me. This is what I had did. Print, select properties, advance, continue, check box - Black ink only. Remember when you decide to print in color you must reset your setting and take out the check from the - Black ink only.