As the most brief and simple way of aiding the student, it will be well to mention those ordinary pigments which it is usually advisable not to mix together.
For mixing with oil color paints, chrome is an undesirable pigment, and it is particularly to be avoided when compounding greens from Prussian or Antwerp blues, which latter colors it would eventually destroy. In such an instance, for common use the best substitute for the chrome would be bright yellow ochre, or, as it is often called, yellow paint. Raw sienna can also be used with the above blue pigments without much detriment to either. In any case where a bright mixed green is absolutely necessary the lemon chrome can be used in conjunction with good ultramarine blue or indigo.
In compounding the secondary color of purple from blues and reds, there is less danger of trouble arising. The best and purest is obtained by mixing ultramarine with madder lake, which is a beautiful crimson and transparent permanent pigment, while lakes derived from cochineal are unstable, ultramarine and vermilion will also answer. Prussian blue and vermilion give very deep purple, which may be lighted up with white. For common purposes, the cheap purple brown is most useful, if required full in strength, but if lighter and pure tints are wanted in oil or distemper, ultramarine blue and vermilion, or, for cheapness, Venetian red, is necessary. Prussian blue in water would not suit so well, but indigo could be used if cost is not a consideration.
The remaining secondary, orange, is not a color very much called for. Orange chrome or orange red is a bright opaque pigment, but otherwise like all the chromes, not a commendable article. Burnt sienna is a very opposite pigment in both nature and source. It is semi-transparent, reliable, and permanent, and is, when of good quality, a remarkably strong stainer, like Prussian blue in this respect. In compounding orange color, the reds and ochres already mentioned are usually bright enough, yellow ochre and Venetian
