Colmar lies between Basel French: Bâle and Strasbourg. There is a direct train connection from both cities. If you arrive from the German side, there is a bus leaving near the border at Breisach to which there is a direct train from Freiburg. The bus-stop is located directly in front of Breisach train station. If you are visiting from Freiburg, it is cheaper to get a RegioElsassTicket, as it is valid for this bus, as well as the entire RVF Regio-Verkehrsverbundes Freiburg network.
By plane
By plane
If you arrive by plane you will probably use one of the closest airports: Euroairport at Basel with a variety of low cost flights or Strasbourg with none. Other airports in the area are Baden Airport, Stuttgart, Zurich and Nancy.