Jean Castro
Jean, what version of InRoads are you using?
Also, does the surface already have a named symbology?
Here is how I got mine to display in different weights and colors:
Tools > Feature Style Manager
I double click on the feature that I want then when the "Edit Feature Style" window pops up I hit the "edit" button in the symbology table. I then edit the correct "Use." You probably want to edit the Plan Line. Be sure that after you change it you hit "apply" instead of just x-ing out. Hope this helps.