Hello HaTeM,

unfortunetly adjusting line colors directly isn't possible yet.
But you could make up a set of color codes declaring which Allplan-standard color is later on depicted in which RGB-color. You can modify the colors in which the lines are printed by using color assignements.

Have a look at the screenshots. I just made a simple light greyish rectangular (color 144) and changed RGB-values. Pay attention to the green text mark. Lines will then be printed in that dark blueish grey.

There is also a short information on this issue to be found in help.allplan.com
see link Plotting layouts

Hope I've been helpful despite my rusty English.

Regards
TG

Edit:
You can save several different sets of plotting-color definitions for example using the name of each company.