Hi
My new mac refuses to print through HP Laserjet 6P. True its old but prints like a dream on PC. (My Wireless HP B110A prints ok on mac with correct drivers).
After several attempts at re installing drivers, tried to get more from Hp but they say only available from Apple - for Yosemite.
Final got it working with basic PCL driver which is good for black only, but any colour prints lighter, but at least I have laser for letters now.
Looking at all the posts there is a driver issue going on.
Hope this might help someone.
Check first for available updates in App store - updates, just in case driver has update.
Go to;
System preferences
Printer and scanner
+ (click add sign)
Click on your printer (under "name" in list as it should be displayed if connected and on).
Go to "use" at bottom of page
Click on your printer which should now be displayed and choose Generic printer if shown, or select software to get a full list of available drivers
Then add and try and print.
Hope this might help somebody until something is done by Apple.