I created a PHP script that checks the HTTP_ACCEPT_LANGUAGE and loads the website using the appropriate language from the 1st two characters:
$http
Do you know if this is happening for all visitors to your site from Colombia? Users are usually free to alter the language settings of their browsers — or to have them altered for them by whoever is in charge of the computer. As zerkms recommends, try logging IP addresses and their headers.
If you have the intl extension installed you can use Locale::lookup and Locale::acceptFromHttp to get a best-fit choice of language from the users browser settings and a list of what translations you have available.
Locale::acceptFromHttp($_SERVER['HTTP_ACCEPT_LANGUAGE']); # e.g. "en_US"