Color obviously is a huge part of the printing process and maintaining consistent color across multiple platforms and stocks is important to keeping customers. A few years back IDEAlliance came out with the G7 System Certification Program which is designed to evaluate the ability of a candidate system to calibrate a printing device to meet the G7 greyscale definition using four 1-D Curves.
Printers need to go through testing procedures and pass basic requirements to become certified. Learn more about the G7 certification process and the other certifications they provide from the link below.
G7 Overview – http://www.idealliance.org/specifications/g7