Additionally, the HSL model defines color within a coordinate space where hue indicates the orientation within a color wheel, while saturation and lightness indicate amplitudes along different axes. Hues are measured within an RGB color space, which is similar to most RGB color spaces, except that shades of white and black are absent. While hue takes an HTML hex color value, it only uses this value to determine the basic color - that is, its orientation around the color wheel, not its saturation or lightness, which are indicated separately as percentage changes.