Cadmium Yellow is a dense opaque yellow pigment, one of the most permanent on the palette and was first introduced in the 1820’s but only slowly became popular due to the high cost in the early days. With time the color range grew from the very pale version that actually contains a significant portion of zinc, to orange which contains a significant portion of selenium. Cadmium Red was developed in 1907 and is co-precipitated Cadmium Sulphide - Cadmium Selenide, the higher the portion of selenium the deeper the red. All varieties of cadmium colors are highly resistant to light and of great importance to the artist.