I need to transfer db from app_1 to app_2
I created backup on app_1
Then ran:
heroku pg:backups restore HEROKU_POSTGRESQL_COLOR --app app_2 heroku
As per the website the addon is depreciated. So that could be the reason for the failure message.
Backups as an add-on has been deprecated.
Since your aim is to move the db from one app to another, why don't you try the instructions mentioned in the link below.
https://devcenter.heroku.com/articles/heroku-postgres-backups#direct-database-to-database-copies