A few years ago I began bringing up hard, sticky mucus. At first it was normal in color, just hard and extremely sticky. A few months ago it started having a bloody color to it, sometimes bright red, others darker. I saw my doctor who first tested me for TB, which came back negative. She then prescribed antibiotics and sent me for a chest xray and ordered a CBC and metabolic count. Everything came back normal except that my blood sugar was a little low. The antibiotics didn't help with the mucus. Now, however, it is no longer bloody but contains black and dark gray spots. I have never been a smoker and do not have asthma.
There is a medication called Mucomyst that actually helps dissolve the plugs. Mucomyst will either dissolve them completely or make them small enough to be coughed up. Mucomyst is administered through a nebulizer treatment either by pipe or mask. Causes of your symptoms could be Bronchiectasis- causes of this disorder may be: allergic bronchopulmonary aspergillosis, Bronchiectasis, cystic fibrosis, repeated respiratory infections, lung tumors, inhaled substances-gases, smoke, noxious fumes, and injurious dust such as coal dust or silica.
Since the chest x-ray was normal, the next test should be a cat scan to try to help determine the cause. You probably need to get a referral to a Pulmonologist, if you don't have one already.
I recommend drinking a lot of water daily to help keep secretions thinner. Taking the mucomyst nebulizer treatments if your doctor agrees, use an expectorant cough syrup, and possible be placed on a different antibiotic since the other one did not help.
I Hope This Helps Good Luck and God Bless.