Having a different icon for a specific email in my Gmail App on Android I have 3 different email accounts under the GMAIL APP on Android.

How could I have a different notification icon for one of the accounts so I know right away if I have email in that account?
As far as I can see the Gmail does not provide this functionality. 

When getting notifications, the app itself decides on what kind of icon is displayed. So unless the app supports setting a custom icon  for notification of a specified account you are unfortunately out of luck.