O what varied answers you will recieve about color and texture on this! lol
Basically it's a more solid chunk of mucus that has been blocking an airway. You know when you cough them out because of thier texture. Thier size can vary from looking like large ground pepper to a large pea.
If anyone has coughed up larger than a pea size, I bow to you now. <img src="i/expressions/face-icon-small-happy.gif" border="0">