Instagram has roll in new feature in its mobile app on Google Play Store. If you download the new update, the App will show you friends who are online with a “green icon” similar to Facebook messenger.
This new feature will show on followers and following lists. It will also show on direct message, DM. On seeing this info, I immediately update my Instagram app to see if this feature is active, however, the green icon didn’t appeared. It is likely my friends are not online at the time.
But the info is real. A source also confirmed this new feature. Adding that, if you don't want the green icon to show on your name, you can toggle it off on the Active status option on Instagram.