YELLOW PIGMENTS
Aureolin, Cadmium Yellows, Chrome Yellows, Gamboge, Raw Sienna, Yellow Ochre, Naples Yellow.
Of these colours, Aureolin is the most expensive, but it is a very beautiful colour, and has the advantage of being permanent. It is sometimes called Cobalt Yellow; it is prepared from cobalt and potassium nitrites.
The Cadmium Yellows are sulphides of cadmium, and are in various shades from pale yellow to orange; they are also permanent.
Chrome Yellows are all chromates of lead, and they darken very quickly in an impure atmosphere, especially when used in water-colour painting. These colours are very cheap, and, at the same time, very brilliant, but they should be avoided in all cases where permanence is desirable. They also produce serious changes when mixed with other colours; for example, a green made by mixing chrome yellow with prussian or antwerp blue is notoriously fugitive in character.
Gamboge is a gum-resin from the East Indian tree Garcimia Cambogia. It forms a bright opaque yellow solution with water, requiring no grinding or mixing in any way, owing to its natural gum. It is fairly permanent and works well in water-colour, but is not quite so satisfactory in body-colour painting.
Raw Sienna and Yellow Ochre are both natural earths containing iron oxide. They are quite permanent.
Naples Yellow is generally prepared by mixing Cadmium Yellow with Zinc White.
RED PIGMENTS
Vermilion, Rose Madder, Scarlet Madder, Alizarin Crimson, Crimson Lake, Carmine, Indian Red, Light Red, Burnt Sienna.