The use of new color pigments that found their way into European easel painting after the Middle Ages, such as Prussian Blue, yellow and green pigments based on the newly discovered element chromium, the copper(II)arsenite pigments Scheele's Green and Schweinfurt (Emerald) Green, as well as blue colorants based on cobalt, such as Cobalt Blue and Cerulean Blue, is explained by means of paintings mainly by the Impressionists.