Well, it's tough to make out some of the specific characteristics with that particular photo. Although they can certainly vary quite a bit just like all other boa's, it doesn't seem to be a Bolivian "short-tailed" boa(B.c amarali)aka from what I can see there. A better, well-lit photo of an entire body shot from above would help more though.
It doesn't seem to be a common boa Colombian boa(B.c imperator) though, and might even possibly be a Brazilian boa(B.c.constrictor), etc...
You should post a better photo of it on the "Boa constrictor" forum and see what kind of responses you get there as well.
Here is a Brazilian red-tail that looks similar to yours.
~Doug
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"a snake in the grass is a GOOD thing" 
