The saddle shape (most -but not all- BCC boas will have peaked saddles that look kind of like this: {}), the tail isn't the deep red seen on many BCC boa babies, and overall head shape and facial markings. For reference, here's a pic of some baby BCC Suri boas (pic at bottom): http://www.riobravoreptiles.com/boas_suriname.htm
BTW Rio Bravo has wonderful info on many boa locales, I'd look through Gus's website.
Colombian BCIs are still considered "red tailed boas" by many (and they're referenced as red tails in pet stores) but personally I don't call my Colombians, Hog, or Argentines "red tail boas" because the "true red tails" are the BCC boas.