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What does it mean when your circles all turn white and how do I get the red, green, blue back?
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It means that something isn't right. The first (and simplest) thing to try if something isn’t working right is to restart your Apple Watch and its paired iPhone. If necessary (device not responding), try a forced restart. Both methods can be found here:
How to restart your Apple Watch - Apple Support
Restart your iPhone - Apple Support
The next steps would be to unpair and pair your watch again and restore from the backup:
Unpair and erase your Apple Watch - Apple Support
Set up your Apple Watch - Apple Support