It is Charcoal which is black when we buy it or when not being used. It gets red in appearance when put in use means to say when burning. And eventually when it's been consumed by fire or after getting burned out or used up, changes into ashes which look grey in color.
There are two types of water hardness: temporary and permanent hardness. Temporary hardness is due to the presence of calcium hydrogen carbonate Ca(HCO3)2(aq) and magnesium hydrogen carbonate Mg(HCO3)2(aq).