The visible spectrum contains millions of colors, but color devices, such as scanners, monitors and color printers can only (re)produce a subset of this spectrum. This “subset” is called a color gamut. The gamut of a device defines the color space it can (re)produce. For example, a monitor can display a wider range of colors than an offset press can print using CMYK colors, while some of the CMYK colors cannot be accurately displayed on the monitor. Each device has a different color gamut.
RGB color gamut
CMYK color gamut
For more information on color gamuts and color spaces, see the Adobe Acrobat Help.