epson cx5800f no print in black only

It's a standard feature of most inkjet printers of all brands. When any cartridge is detected as empty, you have to replace it in order for the printer to carry on working. It's for your own protection because if you don't replace a cartridge as soon as possible, residual ink will dry to a paste in the printhead nozzles.

When that happens, you will end up with blocked nozzles, then you have to waste new ink to clear the blockage. In extreme cases a blockage could even be permanent and you end up having to buy a new printer.

So which do you prefer, buy new cartridges or buy a new printer?
 

spot on. It doesnt matter weather its colour or black, the printer cant perform its built in print head maintenance if any colour is near empty until you replace the cartridge. If you want to use every last drop, buy a laser printer.