I have read that if you also have asthma and/or COPD then you have more mucus. In my case I have asthma and allergies and some days I have a huge (couldn't face using a cup or measuring) amount of thinish varied color from light yellow to green and greenish brown plus lots of nose blowing all day long with or without the saline neb. The amount and color seem to have no effect on my sense of wellness and the pulm doctor said not to worry about it. Other days I don't have much. I am worse when a storm is coming for some reason. Lately I think I am getting bronchospasms (despite albuterol use) from the saline inhalation. I am taking a few days off to see what happens since it seems I am not have trouble getting rid of mucus (though deep down who knows). What causes the excess mucus production in my case is never clear though I think the asthma and allergies cause greater production.