Hi Koos Jan,
I've had a look at the current zip file that I've had online since the first post I made, and can see the "lg_rubber_light_gray" colour defined in both the "LGEO.xml" and "lg_color.inc" files.
Running a test render using this colour seemed to work, so not quite sure why that's not working properly. You've not overwritten your "lg_color.inc" file at all, perhaps?
I've had a look at the current zip file that I've had online since the first post I made, and can see the "lg_rubber_light_gray" colour defined in both the "LGEO.xml" and "lg_color.inc" files.
Running a test render using this colour seemed to work, so not quite sure why that's not working properly. You've not overwritten your "lg_color.inc" file at all, perhaps?