v9.02 on Windows
Netclass nets are always highlighted whether routed or not. I can’t see the metal layer colors of the routed nets! I’d prefer to have only the unrouted nets be highlighted at most.There seems to be no color visibly assigned to the highlighting. Is this a bug? Can the highlighting be disabled?
Kicad version and OS?
Maybe also a user bug 
You may have the wrong setting for “Net colors” in the Appearance Manager.
Select the Nets tab and select Ratsnest or None in the Net Colors. You probably have “All” selected. Observe the different effects.
Version 9.0.x doesn’t seem to have the menu you show.
There is a small note/button in the File > Board Classes menu that says “Set color to transparent to use layer default color.” I selected all the net names in that net class then selected “Clear Color”. This changed the net color to what is usually wanted. I don’t remember having changed the color, but maybe I did and forgot.
Thanks!
Check the “Appearance Manager” in the PCB editor, not the Board Setup.
With “Net colors” set as “All” you will have the problem of the netclass always highlighted. see below:
BUT, with the “Net colors” set to “Ratsnest”, your tracks will show the board layer color and the Ratsnest lines will show as the assigned Netclass color. This can be helpful. See below:
