I wanna agree with Evenstar, I would rough guess 1.5-2 years too.
Colombians are not "true red tails" so when people call their Colombian boa or other BCI localities "red tails" it's not totally correct IMO. The "true red tails" are the BCC boas such as Peruvians, Guyanas, Surinames, etc
Two other common boa confusions: Hog Island Boas are not spelled Hogg with two "g"'s and Colombian boas aren't spelled Columbian with a "u"
Yes - this is what I mean by "Colombian boa". A "normal Colombian" is a normal or wild-type colored and patterned BCI.
And most 2-ish year old Colombian boas are right at about 600-800 grams so yours fits right into that profile.