You've linked your Wave, Wave Mini or Wave Plus to the Hub successfully, but when you wave your hand across the monitors, they no longer show a color, and there is a white ring instead.
This is an issue that affects select users based on the firmware and version of the app that is used, but don't worry, because:
...there is an easy fix!
To get your color back, follow these steps:
Go to your app and select the device which is showing the white ring/dot.
Unpair from this device (NB: this will start a fresh measurement! However your past measurements will still be available on the online dashboard).
Unplug your Hub
Repair with your device with the App
Plug in the Hub
Link the newly paired device with the Hub again, and the color ring should now work.