Email quick filter results confusing

Can anyone explain why colour tags do not appear all the time in the quick filter results when searching through emails?

I use colour tags to organise most of my emails, I also have a couple of saved search folders for finding / grouping certain tags.

But recently using the default quick filter views, whilst I can select the different tags, the results of that filter do not show in the list of emails in the same way at the Main Inbox. Confusingly they show “none”, e.g. when I pick “red”. Clicking into / looking at the filtered emails more closely, they are indeed the red tagged ones. But why in the filtered list does no red appear? What logic is emC applying, I’m concerned my results aren’t correct! (In comparison the filter view of those same emails, or different colour tags, does show the red or yellow.

Can any explain? See pic’s example:




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