Hello,
Please try the below steps ..
- press the SETUP button ( Wrench icon ), then
- press the TOOLS > CLEAN Printhead
You might have to repeat the above steps for atleast 2 times.
If issue still persists, then Please call HP Tech Support for further assistance.
If you are in US , the toll free # is 1-800-474-6836 .
If you are not in US , then log on to www.hp.com , at bottom-left corner there is a world map icon, click on it and then select the region you belong to, which would then provide support options for you for that region.