Are you talking about the “Watch-only” wallet? There are 4 types of wallets you can create in BlueWallet:
- Bitcoin (these wallets appear blue)
- Lightning (yellow)
- Vault/Multi-sig (blue/purple)
- Watch-Only (black/gray)
A Watch-Only wallet lets you view the balance on a cold storage device (for example) and add funds to it from BlueWallet, but not withdraw. This way you can keep your cold storage device locked away somewhere and have safe access to it from BlueWallet. To create a Watch-Only wallet you would import an existing wallet (using a seed phrase) and select “Watch-Only” when prompted.