My machine is hp officejet pro K850

Use your machines built in programme to clean the ink jet heads

should, try cleaning the heads of the one that don't pump ink with achol and swab

Go to paint create black,cyan,megenta & yellow images & print it, observe which colors are not printing,If back missed replace black cartrige, if any color missed out of remain three replace colour cartridge.There is no option to switch off the catridges & printer can recognise the faulty cartridge and it will show on displays.
You can order cartridges online.

Try re-seating the ink cartridges and printing a test page. Those were new HP cartridges, right? Not some garbage from a ink cartridge refiller off ebay?

this is for set up

copy and paste this link in the address bar of your internet explorer and you will know what to do
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01628836&cc=us&lc=en&dlc=en&product=2512009

if you reach service the product that means somethings wrong with the logic card of the printer and you need to replace the printer

pls clean and oiling the catridge rod of your printer.

I read earlier that black and magenta were printing but not cyan or yellow.....HP says to gently wipe the side of the electronic band but not the bottom, I did all of the above...and the printheads carefully, no change w/ the printout from "clean printheads"...the cyan had an occasional blue line(very fine) and there was no yellow.

So I trickled warm water over the cyan and yellow printheads....then thought what the heck, got a bowl of warm water and swished the printheads half submerged. They print perfect now I have the reds, yellows, greens and all the colors back w/ the clean printhead option and printed a coupon, it was perfect.

I hope it's not a short term fix...I developed the problem when I didn't print for a long time, hope this helps someone, Cyn

BTW, I flashed a light down in the recepticle for the cyan and yellow printheads and they were gunky w/ blue and yellow gook, so I clean that out w/ a damp lint free rag....paper towels shredded and I had to carefully remove the remnants.

Go to site below to get your maintenance manual:

http://bizsupport2.austin.hp.com/bc/docs/support/SupportManual/c00501024/c00501024.pdf

Don't forget to rate me.

download the new driver from HP site. And that is it