Chap. CCXLVIII.—General Remarks on Colours.
Blue and green are not simple colours in their nature, for blue is composed of light and darkness; such is the azure of the sky, viz. perfect black and perfect white. Green is composed of a simple and a mixed colour, being produced by blue and yellow.
Any object seen in a mirror, will participate of the colour of that body which serves as a mirror; and the mirror in its turn is tinged in part by the colour of the object it represents; they partake more or less of each other as the colour of the object seen is more or less strong than the colour of the mirror. That object will appear of the strongest and most lively colour in the mirror, which has the most affinity to the colour of the mirror itself.
Of coloured bodies, the purest white will be seen at the greatest distance, therefore the darker the colour, the less it will bear distance.
Of different bodies equal in whiteness, and in distance from the eye, that which is surrounded by the greatest darkness will appear the whitest; and on the contrary, that shadow will appear the darkest that has the brightest white round it.
Of different colours, equally perfect, that will appear most excellent, which is seen near its direct contrary. A pale colour against red, a black upon white (though neither the one nor the other are colours), blue near a yellow; green near red; because each colour is more distinctly seen, when opposed to its contrary, than to any other similar to it.
Any thing white seen in a dense air full of vapours, will appear larger than it is in reality.
The air, between the eye and the object seen, will change the colour of that object into its own; so will the azure of the air change the distant mountains into blue masses. Through a red glass every thing appears red; the light round the stars is dimmed by the darkness of the air, which fills the space between the eye and the planets.
The true colour of any object whatever will be seen in those parts which are not occupied by any kind of shade, and have not any gloss (if it be a polished surface).
I say, that white terminating abruptly upon a dark ground, will cause that part where it terminates to appear darker, and the white whiter.
