Blue light filter switching on & off randomly

The random color-shifting and flickering blue light filter on macOS Golden Gate 27.0.1 that you are experiencing may be a display or daemon glitch.

The 'blue light filter' that you mention is called Night Shift. More from Apple on that:

Use Night Shift on your Mac - Apple Support

Try these troubleshooting steps to stabilize your display:

Toggle or Reset Night Shift

• Open System Settings > Displays > Night Shift.
• Turn it Off or set it to Manual rather than sunset-to-sunrise scheduling.
• Alternatively, toggle Night Shift directly from the Control Center in your menu bar.

Check Accessibility Color Filters

• Sometimes a color filter or True Tone setting gets stuck or misinterprets ambient light sensors after an upgrade.
• Go to System Settings > Accessibility > Display, and make sure Color Filters and related contrast/tint options are turned off.

Restart the SystemUIServer Daemon

If the display process is hanging or crashing in the background, you can force-restart it via Activity Monitor:

• Open Activity Monitor (located in Applications > Utilities).
• Search for SystemUIServer.
• Select it and click the X (Force Quit) button in the toolbar. macOS will relaunch it automatically.

Delete Corrupted Display Preferences

If the preference file is damaged from the 27.0.1 upgrade, you can clear it out using Terminal:

• Open Terminal (find in Spotlight or Applications > Utilities)
• Run the following command to delete the display plist file:

rm ~/Library/Preferences/com.apple.preference.displays.plist

• Restart your Mac to regenerate a fresh preference file

Have you rebooted your Mac? If not, that's the next step. If that does not help, then see if the problem is present when you boot in safe mode. That process performs some system cleanup and clears caches, and also disables 3rd party extensions that may cause problems.

Start up your Mac in safe mode - Apple Support

If that does not correct the issue, test in a new user account. A newly-created user account will have all settings at default, and if the issue does not occur in that new account then it provides guidance on what may need to be changed to correct the issue.

Add a user or group on Mac - Apple Support

Once the testing is complete, the new account can easily be deleted.

Delete a user or group on Mac – Apple Support

Those steps will help to isolate the problem.

barnaby9 wrote:

Thanks for this but unfortunately none of this has stopped it.

Since updating to macOS Golden Gate 27.0.1 (build 26A434), my screen has been repeatedly switching between what looks like a blue-light filter and its normal appearance, approximately every few minutes. I cannot find a setting that explains this behaviour, and it also happens when I connect an external monitor.

I would first check System Settings >> Displays >> Night Shift and turn it off temporarily. 

Apple’s Night Shift guide explains how to change this setting. Although Night Shift makes the display appear warmer, it would not normally explain repeated switching every few minutes.

If the problem continues, check whether True Tone, if available, is enabled, and turn it off temporarily. See Apple’s True Tone guide.

Also check System Settings >> Accessibility >> Display >> Colour Filters and ensure this feature is off. See Apple’s guide to changing display colours on Mac for instructions.

If you use third-party display-management or colour-adjustment software, such as f.lux, quit it temporarily to see whether the problem stops.

If the problem persists, try starting your Mac in Safe Mode. Since a MacBook Air running macOS Golden Gate 27.0.1 uses Apple silicon, follow these steps:

1. Shut down your Mac.
2. Press and hold the power button until the startup options appear.
3. Select your startup disk.
4. Press and hold the Shift key, then click Continue in Safe Mode.
5. Log in and test whether the colour changes continue, including with the external monitor connected.

If the colour changes stop in Safe Mode, this suggests that software loaded during normal startup may be contributing to the problem. 

If they continue, further investigation is needed; this result alone does not establish the cause. 

Restart your Mac normally to exit Safe Mode.

If the problem persists, check for further updates using Apple’s macOS update instructions. 

If none of these steps resolves the issue, contact Apple Support for further investigation.

Because the problem affects both the built-in display and an external monitor, a macOS software issue or a display-management process is a possibility, although this does not establish the cause.

One useful detail to establish is whether the entire screen changes colour simultaneously, including the external monitor, or whether the change affects only particular windows. 

This may help narrow down the cause.

Thanks for this but unfortunately none of this has stopped it.