Is yellow bacteria/plaque indicative of decay?

I’ve recently encountered one of our hygienists who is documenting “yellow bacteria along crown margins, indicative of decay, Dr. to eval”, and then will have the patient follow up with me to have these areas reexamined. This isn’t something I was ever taught, (and so far I have been unable to detect any caries in these areas), but I’m curious if anyone else has heard of this or was taught this?