The masses of light should be of warm colours, yellow or red, supported by blue or grey in the shadows; a very small proportion of which will generally be found sufficient.
The real colour of an object is only seen in the light. All shadows should partake, more or less, of the colour of the light. That shadow will appear the darkest that is surrounded by the brightest light.
The nearer a colour is to the eye, the purer it will appear; arraying itself as it retires, with the colour of the air interposed between it; consequently, the purest colours should only occur in foregrounds,—where the shadows, for the same reason, would likewise be darkest.
The colour of a light will be stopped at the part where any reflex reaches it. We see mountains covered with snow, at sunset, from the effulgence of its rays, make the horizon appear all on fire.
Distant mountains appear more deeply blue, according to the extent of the azure of the air interposed between them and the eye. All masses in the distance partake, more or less, of this quality.
'The vapours mixing with the air, in the lower region near the earth, render it thick, and apt to reflect the sun's rays on all sides, while the air above remains dark; and because light (white) and darkness (black) mixed together, compose the azure that becomes the colour of the sky—which is lighter or darker, in proportion as the air is more or less mixed with damp vapours.'
Shadows produced by the redness of the setting sun, will be blue; from the reflexes of that part of the air not illumined by its rays.
If the sun is overcast, the lights will be general; so will the shadows. If the sunbeams burst out, and strike the objects in a landscape, the shadows will then be dark in proportion to the lights. The brilliant edges of the clouds all assist the general illumination; and all objects in the light, will participate of their colour from reflexion. On the contrary, those parts not included in the range of rays, remain the colour of the air.
The air partakes less of the azure of the sky as it approaches the horizon, being more remote from the sun than that part of it above our heads, which receives a larger portion of its rays. The horizon will be light, while, in ascending to the meridian, it becomes, from this cause, deeper and bluer. So the nature of all colours diminish in proportion as density of air is interposed between them and the eye.
Reflected colours, thrown from, and upon, equal angles, will be the strongest: the most distinct, being produced by the shortest ray.