Oppo has mostly been sticking to its update timeline, though the schedule has gone through a few iterations now, making it harder to follow. You should probably just follow along on the official Oppo community forum for the most recent news.
As per the aforementioned resource, stable Color OS 12 updates based on Android 12 are now officially available for the following devices in the following regions:
If your device is featured on the list you can head over to Settings > Software Update to check whether their unit has received the update. Since this is a staged update, it might take a few hours before ir reaches your unit still.