Some apps require access to make changes to system settings, but this is not security related access to the lock screen or passwords, but to change the ring tone or background, for example.
On the Oppo smartphones with ColorOS, these settings are somewhat hidden deep within the app permissions.
- Open the Settings
- Tap on App management
- Tap on App permissions
- Tap on Set subordinate permissions
- Tap on Rarely used permissions
- Tap on Modify system settings
- Tap on App you want
- Enable or Disable Allow modifying system settings