Four — black, cyan, magenta and yellow, each supplied separately. You replace only the colour that has run out.

They fit exactly the same printers — the XL simply holds more ink. If you print often, 407XL works out cheaper per page and means fewer cartridge changes. For light use the standard 407 may be enough. You can run one of each in the same printer without any problem.

No. Both are WorkForce Pro cartridges and the numbers are close, but they are not interchangeable. Always go by the number printed on the cartridge you are removing rather than by how similar the printer models look.

Epson printers show a message whenever a cartridge that isn't Epson-branded is fitted. It's a notification rather than a fault. Confirm the prompt on the printer screen or on your computer and printing continues as normal. It may reappear after the printer has been switched off and on again.