HEX, RGB, and HSL are different ways of representing a color code. HEX uses a hexadecimal system (e.g., #1db954), RGB uses a combination of Red, Green, and Blue values (e.g., rgb(29, 185, 84)), and HSL uses Hue, Saturation, and Lightness values (e.g., hsl(144, 57%, 42%)).