Unified Inbox lets you manage all your accounts from a single inbox: you can view all of your emails from all of your accounts in a single sorted list.
Each account has a set color to help you identify it. For details, please read more about Account Color Settings.
You can set your default “From” address for sending email from the Unified Inbox by tapping: More (o o o) | Global Settings | Advanced Features | Default Account Settings | Default From in Unified Inbox, and choose your preferred account.
To exit Unified View and select a specific account, tap the account picker in the top left corner | Select your account.