Colors
Black came from atramentum, an artificial substance obtained from resinous wood or grape marc, or otherwise from the calcination of animal bones or organic salts; but also from earth, from which it is exuded like a salt, or from sulphurous coloured earth.
Ph @Cesab1967

Pliny even states that in order to obtain this colour, certain “painters… have violated tombs to steal charred bones, in a deplorable innovation”. The precise composition of the natural ‘atramentum’ of which Pliny spoke is not clear.
Ph @Cesab1967

Among the possibilities are iron oxides, graphite and coal, all readily available, or even lignite, peat and bitumen.
Ph @Cesab1967