Any sane command line program will only output color codes if isatty(STDOUT_FILENO) succeeds.

That can succeed in a number of cases, where it actually isn't a tty with a user on the other end of it. There are a number of internal tools at work that only output logging if there is a tty and thus are run in their cronjobs with a tty. If there were unexpected color outputs in the logs, that would suck since the log aggregators probably wouldn't know what to do with it.