We are planing day trip Colmar to Strasburg via train on Friday. Seems like round trip for two of us is about €64. Should we book in advance or just buy at the station when we are ready to catch the next train. Are these tickets tied to a specific train or can they be used on any train that day. Thanks for clarifying.
The vast majority (maybe all) trains that run that route are regional trains. So the price will not change, no reservations, not tied to a time or train, the tickets are good for that route all day. Also no advantage in buying ahead.
These are "commuter" trains. You can buy at the station or with an app.