This a Blue coloured track for trains, which is visible in Surveyor and invisible in Driver. There are three track colours available.
It is for use under or above water, for driveable shipping, planes or similar. It shows a blue line in Surveyor but is invisible in Driver. In TRS2006, it will show in the minimap for navigation. t matches the purple track included in the TRS2006 release.
Once installed you will find the track as Track Red Invisible Driver in Rail splines in the Australia listing.