For the Brother HL-L3240CDW laser printer, if one of the color toner cartridges (such as the cyan, magenta, or yellow) is empty, the printer will not allow you to continue printing in black and white until the empty color toner cartridge is replaced.

Here are the key points:
- The printer will display an error message indicating that the toner cartridge is empty and needs to be replaced.
- You cannot print in black and white mode if any of the color toner cartridges are empty.
- You must replace the empty color toner cartridge to resume printing operations, including black and white printing.