Black Only button, shown in CLP-300 service manual, is missing on my CLP-300 and user manual.

[Algis]

PROBLEM:   In the CLP-300 service manual, a 'Black Only' button is shown below the 'Stop' button, on the physical control panel of the CLP-300. See photo.
My CLP-300 (built 2007) has only the Stop button on the control panel. The user manual for CLP-300 also shows only one button. Do I have the Beta version or is the service manual wrong?
OBJECTIVE: To be able to print with only the black toner cartridge.  Note:  selecting 'greyscale' will still not allow printing in black if any of the colour cartridges are empty.ges are empty.

[Repairatrooper]

Color printers typically do not allow you to print when color cartridges  are empty because it can cause print quality issues.  The electronics for image formation are calibrated and designed to provide the correct voltages when all cartridges are present. Also continuing to rotate a cartridge when empty can lead to damage if the drum unit locks up due to lack of lubrication or seals cause toner to dump into the printer. The black only button if ever enacted, likely still required toner in all cartridges.