HEX: Uses 6 hexadecimal digits (#RRGGBB) to represent colors. Example: #FF0000 for red.

RGB: Uses red, green, and blue values (0-255). Example: rgb(255, 0, 0) for red.

HSL: Represents hue (0-360), saturation (0-100%), and lightness (0-100%). Example: hsl(0, 100%, 50%) for red.

HSV: Similar to HSL but uses value instead of lightness. Example: hsv(0, 100%, 100%) for red.

CMYK: Used in printing, represents cyan, magenta, yellow, and key (black). Example: cmyk(0%, 100%, 100%, 0%) for red.