if my HP printer is out of black ink can I replace it with color ink? It's an HP Photosmart C4480 with spots for black and color ink cartridges, so if I switch out black with color, will it be alright to have 2 color inks in my printer?
no! colour inkjets like colour laser, operate only when all cartridges are in.
colour inks produce a composite (purplish black), then black cartridge puts the finishing touch on the print.