#1 I would like to render different colors for the different severity events like errors in red color bar in graph. How to provide this in JSON file.
This is not possible today. You cannot do this from charts in the web UI either. We are considering this for a future release.
#2 By default alerts are in disable mode, I would like to know the JSON parameter to make the alert enable.
This is not possible today. Content packs are meant to be generic so they can be applied to any Log Insight instance. Alerts can be configured with either an email address or via vCenter Operations. Both of these alert types would be specific to a particular environment. To enable an alert you need to specify either an email address or vCenter Operations information (again not possible from content pack)
#3 How to provide the mail id for the alert in JSON file?
Same as #2 - not possible.