We always know where daylight has been. It originates at the sun of course, but also we know about its passage through the sky and if it has touched the landscape, another building, a surface, a material with particular colors or finishes, by its color, direction, and intensity.
The blue sky is the result of the scattering of sunlight in the earth’s atmosphere. Atoms of the gases present in the atmosphere (oxygen, nitrogen, hydrogen, etc.), water vapor, and dust, combine to absorb light in ranges other than blue; the blue is reflected to our eyes. This sometimes results in the presence of blue tones in shadows cast on white walls on days of full blue skies. Moisture in the air results in overcast conditions and diffuses sunlight into cold, white light and gray sky; we associate gray and white skies with cool weather and have come to term white, gray, and blue as cool colors, associating color and temperature. Daylight, early and late in the day, travels through more of the earth’s atmosphere, through more dirt and dust particles, reflecting yellow, orange and red light to us. These hues, the colors of fire and of hot, dry climates, have come to be called warm colors.
Light and architecture can employ these strategies with startling effect. At Hans Hollein’s Museum of Modern Art (Frankfort, Germany; 1991) daylight entering a gallery through tall windows on opposite sides of a narrow portion of the building touches large wall surfaces painted dark green and deep orange. The colors are reflected subtly onto white wall surfaces visible around a stair. More directly, in buildings by the Mexican architects Luis Barragan and, later, Ricardo Legoretta, hot, tropical colors are used in remarkably unlikely combinations. The bright blues, hot pinks, yellow and red tones stun the eyes; in the hot sun of Mexican or of tropical climates, the colors may be bleached by the sun. Still, the warm colors appear to amplify the sizzle associated with the heat.