A colour has stopped on a cartridge-printhead model
On these models the nozzles live on the cartridge itself, which is good news: a dead colour usually means a dead cartridge rather than a dead printer. Take it out and look at the copper contacts and the strip of nozzles underneath. Wipe the contacts with a dry lint-free cloth, check the protective tape came off, and reseat it until it clicks. If one cleaning cycle doesn't bring the colour back, replacing that cartridge almost always does, and it's a far cheaper answer than it would be on other brands.