Yellow green mucus means there is a bacterial infection.
The infection is usually an after effect when your body has killed, but the virus has weakened the immune system, leaving the body susceptable to bacterial infection.
In English herbalism, thyme was the traditional cure for all manner of fills affecting the lungs. Culpepper, a famous herbalist who wrote 500 years ago called thyme "a noble strengthener of the lungs, as notable are as grows, nor is there a better remedy growing for whooping cough. It purgeth the body of phlegm and is an excellent remedy for shortness of breath. It is so harmless you need not fear the use of it." His statement is reiterated by most of the classic English herbalists. In traditional European herbalism, thyme was used to treat respiratory infections, laryngitis, tonsillitis, sore throats, irritable coughs, bronchitis, whooping cough, asthma, and catarrhal coughs. Even the U.S. Food and Drug Administration agrees with Culpepper as to the plant’s harmlessness, rating it "generally recognized as food safe."
The actions of the plant include carminative, antimicrobial, antispasmodic, expectorant, astringent, and anthelmintic. Chemicals contained in the herb responsible for these actions include a volatile oil composed of thymol, carvacrol, cineole, borneol, geraniol, linalool, bornyl and linalyl acetate, thymol methyl ether, and alpha pinene. Its flavonoids include apigenin, luteolin, thymonin, and naringenin. Also included are labiatic acid, caffeic acid, and tannins.
One of the plant’s chief medicinally active ingredients is the crystalline phenol called thymol. First isolated in 1720, it was later studied and found to be a rather amazing substance, powerfully antiseptic, both internally and externally. To make matters better, it is an effective analgesic or painkiller. Early on, thymol was shown to kill bacteria on contact so that it found use in surgical dressings and disinfectants for everything from wounds to surgical theaters.