When printing with ArcPress to the HP Designjet 650c, the colors print incorrectly.
The first 650C’s HP shipped only received an RGB version of RTL. These printers are distinguished by an 'A' as the last digit in the model number found on the back left side of the printer. They usually are running version 4.2 of the printer firmware which can be found in Utilities/Statistics/Code rev. This is known as an 'A' controller printer.
HP then changed the color model to CMYK with the release of the 650C 'B' controller printer (last letter in model number is a 'B'). These printers usually run 5.0+ of the firmware.
This printer is not supported by ArcPress for ArcMap 9.x.