Is there a decent train to get from Colmar to Salzburg, preferably a night train as not not waste a lot of time? Looking at beginning of October next year but assumed train times don’t change that much. Suggestions appreciated.
I'm confused by your question. Taking a train from Colmar to Strasbourg is about a 30 minute ride at a cost of 5 to 15 euros, depending on time.
Why would you want a night train for a trip that would be over shortly after you find a seat?
I asked about Salzburg not Strasbourg.
You could take a train to Zürich and board the night train to Vienna there. It stops in Salzburg, but very early in the morning (04:38) so you might not get a full nights sleep, but you could always alight a bit later and take another train back to Salzburg.
Otherwise I think the once daily TGV from Strasbourg to Munich is the best bet.
Back in 2015, we took the TGV train from Strasbourg to Munich, and spent a few days in Munich before continuing by train to Salzburg.
It's a little further than I like for one day's travel but the route that seems logical to me is Colmar to Heidelberg, Heidelburg to Munich (what I see routes through Frankfurt and takes a little over four hours) and Munich to Salzburg. Changes included, it's about five hours. Salzburg is a short train ride from Munich and is considered part of the DB area (in case you are using any type of pass).