Europcar (At the Airport) : + 33 3 89 20 85 70
http://www.europcar-est.fr/villes/location-voiture-colmar-aeroport.aspx

Hertz (In the city Center but possibility to pick up/out the car at the Aiport) : +33 3 89 41 18 41

https://www.hertz.fr/p/location-de-voiture/france/colmar?utm_source=google&utm_medium=local&utm_content=CMRC63&utm_campaign=GMB-Listings

And many others...