HP DesignJet Z2600 colour issues

[seascape2]

I haven't used my printed in a couple of months (as is the norm as I use it about 4/5 times a year in time for trade shows). Today I'm trying to print design work and the colours are not coming out right...not bright enough and not strong enough. I've replaced the ink cartridges even though they weren't empty, cleaned the print heads, done a diagnostic test and it all looks fine. HP can't help me for some reason. couldn't really understand why but maybe I need to get a local engineer out to look at it. Hoping someone can help me figure it out as the colours are almost there but not quite. 

[Valsimot]

From the printers menu, print a print quality page, scan it and post here.