You have my sympathy - this is difficult.
The printers most firms use for drawing output don't have the gamut necessary to accurately reproduce color.
Archicad doesn't make a file compatible with what are called "color spaces" in printing lingo. Once you convert to PDF, the process gives the file a color space understood by the printer.
Your best bet for accuracy is with a photographic quality printer - like the Epson 3800 or 4800 - and top quality paper.
I have been working with a firm that attempted to calibrate their system [for flat colors on Archicad analytical elevations] and the result was far from perfect.
I suggest continuing with the PDF approach.
Dwight Atkinson