Hi Gil,
It appears you may have a blocked drain hose or a defective pump. When the heads are parked and the capping stations are in contact with the heads, the hoses to the drain bottle allow a small amount of air into the capping station to 'break' any siphoning action on the heads.
Since two colour heads are integrated into one head assembly and are sharing one capping station, if one of the two has more ink in its cartridge than the other, the ink will attempt to equalize levels between the two cartridges. By allowing a small bit of air into the capping station from the drain bottle, this equalizing action will not occur.
Use a syringe to draw air through the various sections of drain hose and through the pump. If air can't be drawn through any section, this will indicate a blockage.
The original VersaCAMM pumps were the cause of many printing problems. The original pump had two separate chambers, one for each capping station. Roland now have a new style pump that is much more reliable. The new pump has one chamber so the drain hose from both capping stations are 'tee'd' together before the pump and there is only one hose from the pump to the drain bottle.
If you still have the original two chamber pump, it is likely the source of your problem. The pump change is easy and can be completed by you if you're somewhat mechanically inclined.
To clear the ink line of the wrong colour ink contamination, keep printing the 3" X" blocks of Black (C,M,Y = 0%, K=100%) until the Black prints cleanly again. Since this problem only started today, this will also reduce the likelihood of the Cyan actually making its way all the way into the Black cartridge, thereby contaminating the Black cartridge and making it trash.
As preventative maintenance, your heads should be manually cleaned (with swabs and cleaning fluid) at least on a weekly basis. Along with manually cleaning the heads, the wipers and capping station tops should also be swabbed and some cleaning fluid should be poured in each capping station which will help to prevent blockages in the drain lines.
All the best!
Mark
