Could be marked distant area that is using different pens.
You can either set one pen for this or let ArchiCAD make them 'lighter', which assigns (in my opinion) 'random' other pens. For my penset I have figured out which pens gets changed to which and adjust the pen weights and colour accordingly.
Erwin Edel, Project Lead, Leloup Architecten
www.leloup.nlArchiCAD 9-26NED FULL
Windows 10 Pro
Adobe Design Premium CS5