Your printer will alert you when a toner cartridge runs out, and will let you know on-screen which colour needs replacing. The on-screen steps will guide you through the process, here is an example of how this looks for Toshiba models e-STUDIO 5518A/6518A/7518A/8518A.
When you use a replacement cartridge, or are running low, make sure you let us know so that we can bring you more spares.
Do not touch the terminal of the toner cartridge. This may cause the equipment not to recognise the toner cartridge or may damage the terminal.