The same gradation takes place in all the juxtapositions of colours distinctly separated. I believe that attention to these principles, and especially a perfect knowledge of the consequences of the last three, exercises a very happy influence upon the art of painting, giving to the artist such a knowledge of colours as he cannot possess before the law of their simultaneous contrast and its consequences have been developed. Among the details which the painter endeavours to render, there are many which, due to contrast, either of colour or of tone, must be produced spontaneously. I presume that the Greek painters, whose palette was composed only of black, white, red, yellow, and blue, and who executed so many pictures which their contemporaries have spoken of with intense admiration, painted conformably to the simple method of which I speak; _devoting themselves to great effects_, _many small ones resulted from them_. _Utility of the Law in order to Harmonize those Colours of a Composition which are Inherent to the Nature of the Object represented._ 324. In all, or nearly all, compositions of painting, we must distinguish the colours which the painter is under the necessity of using, and those which he may choose, because, unlike the former, they are not inherent to the model (313). For example, in painting a human figure, the colour of the flesh, the eyes, and the hair, are fixed by the model; but the painter has a choice of draperies, ornaments, background, &c. In an historical picture, the flesh colours are, in the majority of the figures, at the choice of the painter, as are also the draperies and all the accessories, which can be placed and imagined according to his judgment. In a landscape, the colours are determined by the subject, yet not so arbitrarily but that we can substitute for the true colour that of a neighbouring scale; the artist may choose the colour of the sky, imagine numerous accidental effects, introduce into his composition animals, draped-figures, carriages, &c., of which the form and colour may be so selected as to produce the best possible effect with the actual objects of the scene. 325. A painter may also choose a dominant colour which produces, on every object in his composition, the same effect as if they were illuminated by a light of the same colour, or as if they were seen through a coloured glass (259). 326. Although the law of contrast affords different methods of imparting value to a colour, genius alone can indicate the mode in which this idea should be realized in a painting.