A good recent article.
https://www.the-microbiologist.com/news/colour-of-phlegm-can-predict-outcomes-for-patients-with-bronchiectasis/1530.article
My doctor told me the phlegm colour wasn’t important. That’s universally accepted as wrong advice now when there are other symptoms. The most important indictator though is the thickness of the sputum.

Some people continue to have some coloured sputum without infection but I suspect it is the chronic inflammation that might wane every now and then.
Good luck!