There are two updates plus patches for both new versions of Trainz since TRS2006. Look TS2009 and the new TS2010. TS2009 has had a few service packs with a fourth one recently added and TS2010 is on its third service pack.
Railroads use various combinations of signals including the red, green, yellow, and even white (lunar). American and Canadian, I'm not sure about others sometimes include a blinking yellow in addition to the others to indicate slowing down or some kind of restriction. In Trainz the signalling is simplified, but very operational. In general trains will operate at full speed with all greens, half speed with a yellow, and stop at a red.
There are also other combinations of signals when two heads are used such as red over green and red over yellow. Both allow for movement even with the red and red yellow, but they mean different things from stop.
Recently someone posted another thread on signaling. Check out the links in there as they are helpful.
