Perceived graininess is one of the most important image artifact attributes to describe the image quality of a printing system. Although a international standard, ISO13660, defines the perceived graininess on a monochrome image, rapid prevalence of color printing systems in recent years significantly increases the demand for a color granularity metric which correlates with visual assessment in the color space. We propose to adopt flatbed scanners to efficiently capture high-frequency color noise. The perceived noise is then mapped to the visually uniform CIEDE2000 color difference space. Consequently, a psychophysical experiment will be conducted to evaluate the perceived grain on patches with various colorants. At last, we will propose a color granularity metric to best describe the obtained color grain perception.