In general, the further north one goes, the earlier the peak color. Surprisingly, though, Sand Patch on the Capitol Ltd sees peak color about 2 weeks before I do in Western Massachusetts. I haven't done it, but I'd guess the Vermonter would be a good 'color' train, but finding a hotel during leaf-peeping season for this year will be difficult and/or expensive. Depending on how long you'd like to drive, Conway Scenic RR in northern New Hampshire would be a sure winner.
The trick, however, is timing. Being there a week too early isn't too bad, but a week too late, you've wasted your time and money. Currently for western MA, the TV weather forecaster is saying peak season will be mid October rather than early October. We already have portions of a small percentage of maple trees turning, so I think the weather guy is dead wrong. I'm sure there's some websites that would show up on Google that can more accurately predict when and where the best color will be.