It is used for large solid areas. Small text should use single-ink black to avoid blurry edges from slight misregistration.
Color
Pantone
A code such as PMS 185 tells printer and designer exactly which color is intended, regardless of device.
CMYK
Inks are layered as tiny dots to build full-color images. Files should be set to CMYK before printing for predictable color.
RGB
RGB can show brighter colors than CMYK ink can reproduce. Converting an RGB file to CMYK often makes saturated colors look duller.
Spot Color
Pantone Matching System (PMS) is the best-known spot color library. Spot inks help brands match a logo color exactly.