Colombian and Argentinian Tegus are extremely different creatures...
I have a 3 year old Arg Tegu. 50" 12 lb male. He's awesome. By far the most docile reptile I've ever seen. He's fairly lazy most of the time but eager to adventure when he get attention. He is happy to lounge in his enclsoure, bask on the balcony, explore the yard or visit a pet shop. All free roaming without a leash of any sort. I am active on my Tegu's breeder's forum (TeguTalk.com) and it seems there are a whole lot of Arg tegu owners that have experiences similar to mine.
I had a Colombian Tegu for a short time abotu 20~25 years ago. It was a holy terror. It attacked everything put into the enclsoure. I was young at the time (about 13) but had kept several reptiles for a couple of years at the time, but there was no way I could have tamed that beast. The pet shop took it back...
Looking back, I suspect it was a newly arrived wild caught baby. Because that was the standard back then, Colombian Tegus earned a bad reputation. But keep in mind they well deserved it! More recently a small number of Colombian Tegus are captive bred in the US and most of the imports are farm bred and captive hatched/raised.
I would personally be very cautious and ensure you are not buying a wild caught Colombian Tegu, they are well known to be extremely aggressive... ideally I would search out one that was captive bred. You will pay a bit more for it but it will likely be worth the investment... But most will be farm bred/captive hatched. These will come with some risk as their attitude is common to be within a wide range. Anything from easily handalable to extremely aggressive...
Also keep in mind even a Columbian can become a 5~8 lb 2.5~3' mass of jaws and claws... so choose wisely...