10. In like manner, if we look upon red, green is formed in the eye, and is cast upon adjacent colours; or, if we look upon yellow, purple is formed.
11. Harmony results from an agreeable contrast.
12. Colours which perfectly harmonise improve one another to the utmost.
13. In order to perfect harmony, the three colours are necessary, either in their purity or in combination.
14. Red and green combine to yield a harmony. Red is a primary colour, and green, which is a secondary colour, consists of blue and yellow--the other two primary colours. Blue and orange also produce a harmony, and yellow and purple, for in each ease the three primary colours are present.
15. It has been found that the primary colours in perfect purity produce exact harmonies in the proportions of eight parts of blue, 5 of red, and 3 of yellow; that the secondary colours harmonise in the proportions of 13 of purple, 11 of green, and 8 of orange; and that the tertiary colours harmonise in the proportions of olive 24, russet 21, and citrine 19.
16. There are, however, subtleties of harmony which it is difficult to understand.
17. The rarest harmonies frequently lie close on the verge of discord.
18. Harmony of colour is, in many respects, analogous to harmony of musical sounds.
19. Blue is a cold colour, and appears to recede from the eye.
20. Red is a warm colour, and is exciting; it remains stationary as to distance.
21. Yellow is the colour most nearly allied to light; it appears to advance towards the spectator.
22. At twilight blue appears much lighter than it is, red much darker, and yellow slightly darker. By ordinary gaslight blue becomes darker, red brighter, and yellow lighter. By this artificial light a pure yellow appears lighter than white itself, when viewed in contrast with certain other colours.
23. By certain combinations colour may make glad or depress, convey the idea of purity, richness, or poverty, or may affect the mind in any desired manner, as does music.
24. When a colour is placed on a gold ground, it should be outlined with a darker shade of its own colour.
25. When a gold ornament falls on a coloured ground, it should be outlined with black.
26. When an ornament falls on a ground which is in direct harmony with it, it must be outlined with a lighter tint of its own colour. Thus, when a red ornament falls on a green ground, the ornament must be outlined with a lighter red.