Risograph inks are soy-based and do not conform exactly to any color standards. The listings below are approximates for reference only. Additionally, Riso inks are also slightly transparent and allow for variations in overprint and based on the color of paper they are printed on. 

Mac OS X Printers & Scanners Panel Showing a Riso RP Printer

There are no Riso-supported Mac OS X drivers for the RP Series, yet it is possible to print directly to an RP machine from Mac OS X, without complex tinkering –if any at all– or extra files. All one needs to do is install Riso drivers from a different series that do have OS X support, then connect your RP to your Mac via Ethernet or USB and create/add your printer in the exact same way you'd add any supported printer under Mac OS X.