"colloquial" has no place in official contexts. I'll happily talk about kB and MB without considering the small difference between 1000 and 1024, but on a contract "kilo" will unequivocally mean 1000, unless explicitely defined as 1024 for the sake of that document.
> on a contract "kilo" will unequivocally mean 1000, unless explicitely defined as 1024 for the sake of that document.
If we are talking about kilobytes, it could just as easily the opposite.
Unless you were referring to only contracts which you yourself draft, in which case it'd be whatever you personally want.