Autodesk AUTOCAD 2006, Command Reference Manual, Page: 505 / 1490

Enable Fog
Turns fog on and off without affecting the other settings in the dialog box.
Fog Background
Applies fog to the background as well as to the geometry.
Color System
Controls whether the red, green, blue (RGB) color system or the hue, lightness,
saturation (HLS) color system is used.
Hue, Lightness, Saturation
Adjusts the individual hue, lightness, and saturation components of the
selected color. The result is displayed in the Color Selected swatch.
Moving the Hue scroll box changes the color. Moving the Lightness scroll
box increases the luminance or brightness of the hue by adding white.
Moving the Saturation scroll box to the right increases the purity of the
color. The higher the saturation, the less gray in the color.
Fog/Depth Cue Dialog Box | 481