The window below appears when black ink runs low and there is more color ink than black ink. It appears only when plain papers is selected as the paper type, and Text is selected as the Quality Option.
The window gives you the option to either continue using black ink normally or conserve black ink by using a mixture of color inks to create black.
Click the Yes button to use a mixture of color inks to create black. You will see the same window the next time you print a similar job.
Click the No button to continue using the remaining black ink for the job you are printing. You will see the same window the next time you print a similar job, and again have the option to conserve black ink.
Click Disable this feature to continue using the remaining black ink. You will not see the window again until you replace the black cartridge.