You can have one custom scheme per language binding. When you first create them they are saved to %appdata%\SoftVelocity\Clarion\10.0\modes or, if you are starting your IDE with the /configdir switch then you should know where to locate that same modes folder!
If you have one you would like to share please reply to this topic and attach it! (or create a GIST or whatever your preferred code sharing method it of course).
My basic changes are the background color, the intensity of the highlighted line and the color of the parameter names in the XML doc comments. Possibly other I can’t remember now.
The requested URL was not found on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.