The duct and pipe system family types have the ability to override the graphics display for the line styles of ducts or pipes using that system (colour, line type, weight etc).
It would be incredibly helpful if you could also set colour fill overrides in the system properties as well. For our drawing standards, we have a thin black outer line on duct and pipe, and then a different colour fill depending on the system type. Currently, we have to have a separate filter for each system type, and then add that with a colour fill override to every view template. This gets very time consuming and tedious to manage, and is not very flexible for adding new system types.
Adding this to the system type properties like the line graphic overrides would be a massive help with this and mean there is only 1 source to deal with