GCR is a sophisticated Color Separation technique that identifies the neutral gray component of a color, which is made up of equal parts of CMY, and replaces it with the equivalent amount of Black (K) ink. The key difference from UCR is the scope: GCR applies this replacement across the entire tonal range (highlights to shadows), wherever a gray component exists.

This comprehensive approach ensures that neutral colors are consistently built with the more stable Black ink, not the three less predictable CMY inks. This leads to a massive improvement in the stability of gray balance, significantly reduces the consumption of expensive CMY inks, and helps manage Total Ink Coverage throughout the entire file.