Hi James,
I have noticed in the demo game, that I cannot choose Blackpool liveries for the trams. Now they are correctly painted with the austerity livery, but it should be possible to switch them to blackpool liveries. I checked simuconf.tab, and did not find anything unusual, unless there is some limit on number of livery schemes... Blackpool is #32, and there are many more, which I do not see in the game.
The issue is that the livery schemes are saved with the saved game, and the saved game in this case is rather old. If you start a new game, you will see all the liveries present.