Only in RGB mode is 16 bits per channel available. RGB is my default working mode. An RGB image contains three channels made up of Red, Green, and Blue color data as shown in the sample below. RGB output mates well with the monitor RBG electron guns. The direct color match can produce excellent color on the monitor screen.
Professional monitors are pricey but they can be tuned or matched to very precise output settings.
CMYK Color Mode CMYK is designed to convert well into the printer's environment with its four-color plates of Cyan, Magenta, Yellow, and Black. Counter Intuitive CMYK contains 1 more channel than RGB but it has a smaller color gamut. Its color gamut is designed to meet the narrower color range needs of the four-color printing process. 24 Channels Except for the Bitmap-mode image, all images in Photoshop can have up to 24 channels. These are frequently called alpha channels.