That question, when addressed to 2 different pulmonologists, was met with a "maybe" - each said color TENDS to indicate possible infection activity, but not always. And when my original diagnosis of both severe pseudomonas and MAC was made, my mucus was very thick and sticky, but only a very pale yellow. That doc was surprised by the pseudomonas. And even more surprised that the MAC grew in the lab in less than 4 weeks.
On the other hand, if I get a sinus infection, my mucus is immediately dark-green/brown and smelly.
So I guess that, as with everything related to Bronchiectasis, it depends on the individual and their lungs and other ailments.