English: Geometric Representation of Colours: Isaac Newton arranged the colours in the form of a triangle, as shown in fig. 21. If we place three of the spectral colours at three angles, thus—green, violet and red—the sides of the triangle include the intermediate colours of the spectrum, except purple. The point S corresponds to white, consequently, from the intersection of the lines which join the complementary colours, the straight lines from green to S, RS and VS represent the amount of green, red and violet necessary to form white; the same holds good for the complementary colours; for example, for blue and red, the line SB = the amount of blue, and the line SR = the amount of red required to form white. Again, any point, say M, on the surface of the triangle, will represent a mixed colour, the composition of which may be obtained by mixing the three fundamental colours in the proportions represented by the length of the lines M to green, MV and MR. But the line VM passes on to the yellow Y; we may then replace the red and green by the yellow, in the proportion of the length of the line MY, and mix it with violet in the proportion of SV. The same colour would also be formed by mixing the amount MY of yellow with MS of white, or by the amount RM of red with the amount MD of greenish blue.