Light and color have historically been closely integrated with architecture and design, as they can completely change a viewer’s perception of form and space. Color around us is the simple consequence of reflected or transmitted light. It is not a characteristic of an object without light.

In Monet’s study of the Rouen Cathedral, his painting series depicts a perception of the Cathedral that dramatically changes as the lighting quality and colors vary. These different perceptions of the same Cathedral are due to the reflections of light, color, and relative brightness of the architectural form, caused by varying daylight conditions.

Light is a very descriptive tool: it creates shadow and depth, defines edges and boundaries, renders objects and people, and informs us of the conditions of our surroundings. With shifts of light, brightness/contrast ratios, and changing reflections, the “image” of the space transforms. This image or “perception” of space is an important biological need for humans, giving us not only the ability to perform specific tasks within that space, but also the important quality of visual, aesthetic, and psychological comfort.

Appropriate color of light is very important to the quality of lighting in a space. As humans, we have developed subjective expectations of what is appropriate, based upon previous experiences that have been mentally compiled. We process our visual field in comparison to other spaces that are “pleasing,” as well as to what we know of the exterior environment of that particular time of day or season. It’s important to recognize the change in color and intensity of light, from day to night and summer to winter, in artificial lighting designs, as those expectations are firmly set in our circadian rhythms.

The Amenity Curve, developed by A.A. Kruithof, illustrates the idea that a “visually pleasing environment” is directly related to the “expected” color temperature of the light source. Typically, we expect lighting color temperatures in the warmer range for spaces with lower overall light levels, such as residential environments or lounge areas, whereas cooler color temperatures are expected for more public spaces that require higher light levels. “Warm” refers to light color temperatures between 2700K to 3000K. Incandescent sources are rich in red and yellow, which is similar to the familiar light of the sun, and of common candle flames. “Cool” refers to light color temperatures between 3600K to 5500K. These color temperatures are more closely related to the bluish color of skylight, around 6500K.

When our visual expectations and our need for information are satisfactorily met, then our environment is perceived as appropriate and comfortable, meaning that we measure “comfortable” lighting not by a strict allowance of footcandles, but as a balance of brightness and contrast throughout a space that meets our expectations, both physically and mentally.

These principles of light and color in architecture are the means by which architecture expresses its form and function to its occupants. Light communicates visual information to the viewer, and establishes how we perceive our environment.