Refilling HP deskjet 930c cartridges

[Rolyrocks]

I have WH Smith H78a colour cartridges which I have refilled for use in A HP Deskjet 930c printer. The empty light still flashes and the pointer still says clour cartridge empty. I ahve done previously with black cartridge and it worked O.K. It Has only been empty 24 hours.
Any advice?
Roly.