Ian,
Two added bits of information:
1. Having made the 'invisibility' changes Surveyor, there is one scenario where the red/green arrows will stay permanently visible. It is when you have the Track flyout open, with the Trackside button selected. Changing to one of the other two buttons in that flyout, (or to any other flyout), will make them disappear.
2. When they are in 'invisible' mode and you want to quickly see which way a junction is set, just float your cursor over it and all will be revealed.
Cheers
Casper