Femi,
You seem to be thinking about this the wrong way round.
Each pen number is usually used for the same specific purpose on each pen set generally. For example pen no. 27 (on mine) is always for cut structural walls, pen 23 always for openings. What colour you want each pen is entirely down to the purpose you need it for.
If you need a pen set for drafting/modelling you would usually want each type of element to have a different contrasting colour. This helps you to see at a glance whether you are using the correct pen for the purpose, and clearly defines the different types of elements on plan.
When you want to print a plan, you should set the drawings to use a printing pen set that generally has most of the pens set to black. You would not generally use this pen set to draft/model with.
You can also set up different pen sets to highlight or emphasize any particular information that you want to convey. Maybe setting all the structural walls to be outlined in bright red, for example. This can be done by simply copying the printing pen set, and then changing the pen for the structural walls to red and increasing the thickness.
This arrangement gives a lot of flexibility in how things can be displayed without having to keep changing the individual settings of all the elements.
It sounds like you want to set up a high contrasting pen set for modelling purposes. Simply set up a pen set where the
use
of each of the pens stays the same but the colour is different. Simply double-click on any pen in the pen set to launch the colour chooser, and you can type in the RGB in the three boxes marked Red Green & Blue on the right.
My apologies if you know all this already
. This is a fundamental part of outputting drawings in ArchiCAD, and you should have it absolutely clear in your head how it works before commencing any major work, as correcting it may be complex!
I hope the above ramble may be useful to you! Best of luck!