Yes, as a temporary feature (?) in the SGI version:

If you want to use fancy colours for your maps and molecules, for example when you are taking slides, try the Screen_colour command in O. On ESVs, this enables you to change the background colour of your O window.

However, on an SGI, instead of changing the background colour, this command starts an SGI utility program called 'cedit'. It comes up in a small window; make this window a bit bigger and use the LEFT mouse button to change the Red Green and Blue components of your colour the resulting colour is displayed on the right. When you have found a nice colour, read the three numbers at the bottom of the window, e.g. 222 21 108.

Now go back to your O terminal window, and execute a command that requires you to select a colour (e.g., map_par or paint_colour).

Now the big trick: when O asks for a colour you DO NOT type an exotic name such as brownnose_beige, but instead you type the three numbers and ... VOILA !

Note: sometimes you can't use three RGB numbers, for example inside ODL objects. In those cases, use the following trick:

  O > map_par ; ;
 Map> Colour? [rgb]: 35 109 162 ; ;
  O > wr .map_integer ;;
.MAP_INTEGER              I          2 (10(x,i7))
 3648767       1

Now, O has done the conversion between RGB and single-number O colour for you; the result is stored as the first item in the datablock .MAP_INTEGER, in this case 3648767