Any way to revert to yesterday's label colors?

If you changed label colors and want to get back to the defaults, there are two things to check, depending on where the change happened.

Project panel label presets
If you changed the label colors via Settings > Labels, you can revert to the system defaults by clicking Label Color Presets and choosing Default.

This restores the default label color set, but it does not undo individual label assignments already applied to clips.

Timeline label display
If the colors look wrong only in the Timeline, click the Timeline Display Settings (wrench icon) and enable Show Source Clip Name and Label.

This forces the Timeline to display label colors from the Project panel. Any label color changes made in the Project panel will then automatically update in the Timeline.

It is not really reverting to a previous state, but my (paid) extension Automation Blocks for Pr offers tools to batch-update the label colors in your project. Get started here https://docs.mamoworld.com/automation-blocks/tools-pr/projectItemsTools#labelColors

If you just need it once, you can even do it with the free trial.