The bug has reportedly affected at least Apple Watch SE and Apple Watch Ultra models. After the update, the clock screen tone turned green. This is especially noticeable on the black background of the password login screen, in the control center, and when viewing notifications.
For some users, the error went away after the gadgets restarted. Most likely, the problem is not with the device itself, but with the software.
Most likely, a bug fix will be released in a future watchOS 9.6. However, it is still unknown when this version will be released.
Source: Ferra

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