Hi, I was about to change one thing or two about the railcargo set, when this issue came to my mind.
There are some problems that make the decision not that straightforward.
Given the multiplicity of wagon generations, if I were to make 5 versions of each would mean ultracrowded depots.
My oppinion and point of view on the subject is that, given that the locomotives are player coloured, and that there are cabooses available, wagons shouldn't be player coloured (In the US set, at least), but, do you really find any difference between 6 hopper and 3 hopper generations? It's kinda crazy to have a different hopper every 20 years, and game-wise, it's nice not to have a perfect gradation of capacities and weights. For example, I wouldn't like to see a diesel locomotive for every n*500kW of power and another variation for every n*40km/h. That doesn't make real sense.
Counting early wagons, (XIX century, that is), I'm about to reduce drastically the playercolourcrowdiness of your depots, and add some colour and joy. Poll, perhaps there's a better idea around.
Oh, and of course, a player colour version of each wagon will be provided, just in case.