As far as I'm aware, a job can currently complete only with "Success" (green) and "Failed"(red). There are plenty of situations where a job should not fail, but provide a warning (yellow). For example, a security scan of a potential vulnerability should not block a build, but provide a warning to the developer that something is worth checking out (could be a false positive). This could be implemented by reserving a specific exit code as a warning or some other way.