I am using the latest Beta of Sierra and since installing it have found oddities with my HP Envy 120.
Printing became extremely faded when printed from the iMac but perfect when printed using the diagnositc tools from the printer itself.
This suggests to me it is OS related rather than the printer malfunctioning.
I have also put in new ink cartridges.
I have searched and cannot find any known issues with the latest Beta of Sierra for this problem.
I have also removed and re-installed the printer from freshly downloaded drivers and still the same.