two columbians can be housed in the same cage as along as there is enough space and they are the same size. If they are new to each other then you have to interduce them slowly to help avoid fights. If you check out either tegutalk.com or thetegu.com (i think your already a member of thetegu) there are alot of treads about the best way to interdoce tegus in the breeding and gentic section.

Good luck!