These settings are similar to models "7" and "8", except that the background color will be gray instead of white. This is useful if you want to use 3-D-LINES and want to eliminate intensity considerations.
Equivalent settings
COLOR-MODEL "9" is equivalent to Color-Trans "3", Intensity-Flags "193".
COLOR-MODEL "10" is equivalent to Color-Trans "1", Intensity-Flags "193".
See Appendix H, Book 4, "Appendices" for details.