0-15 appear on the color bar

16-20 are system colors extracted from the Windows Display Properties, Appearance settings. Modifying these colors in this dialog box will only affect the CC3 display environment. They will not affect the appearance of Windows or other applications. Specific color assignments:

16 button face color

17 button text color

18 button shadow color

19 list paper background

20 prompt text

31 is the "no change" color. Entities drawn using this color will be drawn in the same color as the prior entity. This can be useful when defining arrowhead symbols. If the arrowhead symbol is drawn, a line command immediately following will use the color of the arrowhead. When a symbol has more than one color, the color used to draw the last entity in the symbol will be used.