The Green App is a Splunk App to provides a utility to generate a Green alert once after the issue is resolved. And also regenerates as long as the issue is present. Usually with Splunk alerts, you create an alert when there is an issue with the system which is very easy to do with Splunk but then you are requested to also create an alert when that issue is fixed, but you need to generate that only once after the issue is fixed. You could use this App in those scenarios.