If you have issues with only one train spawning, that is usually caused by insufficient signals (trains won't spawn if the spawn area path is occupied).

Colourable would require remaking the textures, and it would probably break existing trains (the colours, the functionality would be fine)

Love it! Been using it on my underground metro lines. I do have a problem with only one spawning on my lines at any time but a different line has multiple of them running at once so I assume it's nothing to do with this train. is there any chance they could be colourable, however?

Ooooooh.