Hex color is a way to represent colors using a six-digit hexadecimal code, commonly used in HTML and CSS. It starts with a # followed by two-digit pairs for red, green, and blue (e.g., #FF0000 for red). Each pair ranges from 00 (0 in decimal) to FF (255 in decimal), representing the intensity of that color component. Hex colors are compact, readable, and widely supported in web design. For example, #00FF00 is green, and #000000 is black.