You may see this color staining for a couple of weeks off and on, it is due to pigments collecting in the lines that run from the cartridges to the print head itself. When you start your printing for the day after the printer has been sitting for a time, run a nozzle check to see if you can see any visual color staining, if you can, run a Cleaning cycle through the control panel and do another manual nozzle check. Sometimes it will take 1 cleaning cycle, and sometimes it might take 2-3 to clear the staining. Obviously the more ink you run through the system the less staining you will see and at some point (it probably won't take long with a new system) it will be gone completely and you won't have to do this procedure anymore.
The Capping station is where the print head releases the ink to keep the nozzles firing in the head, it is surrounded by a runner seal that seals around the print head when it's running through it's automatic cleanings OR you've performed a manual Head cleaning through the control panel or utility. Sometimes when the capping station has become gummed up with pigments it can transfer the old pigments to the head when it runs the cleaning cycle, this is due to the residual pigments that are left behind in the capping station not being sucked completely down the pump to the waste tank. It does help to clean the capping station when you are switching over to a different ink set to help assist with the removal of the old pigment inks.
To do this on the 3880 you will have to turn the printer ON, wait for the head to move off the capping station to the left of the printer, then quickly unplug the power cord. You will now have access to the capping station, using Piezoflush or Distilled water, take your syringe and squirt a small amount of either fluid into the capping station, let it sit for a few minutes then dab it up with a paper towel that's folded in halves. You can watch this video on the R2880 and apply the same method to the 3880 for this procedure https://www.youtube.com/watch?v=eUysQFDH6u0
Glad to hear you are enjoying our system and I definitely recommend purchasing the Jon Cone Type 5 papers if you think the Harman paper is nice, you will really enjoy the Type 5 paper, it is a lovely paper with very nice gloss compatibilities using just one pass of 30K GO.