HSL (Hue, Saturation, Lightness) color model is a way to specify colors. 'Beautiful' as an adjective could refer to a color that is pleasing or attractive to the eye. To describe a beautiful HSL color, you might use values that represent a high degree of saturation and lightness, avoiding extreme values that could lead to a color that is too dark or too bright. For example, a beautiful HSL color could be one with a hue in the green range, a high saturation, and a moderate lightness, such as HSL(120, 70%, 50%).