The following code should work:
function Test()
{
var regEx, Matches;
var InStr = "Text 12:11:12";
// Set regular expression pattern
regEx = /\d*:\d*:\d*/ig;
// Perform search operation
Matches = InStr.match(regEx);
// Iterate through Matches array
for (var i=0; i<Matches.length; i++)
{
Log.Message(Matches[i]);
}
}