Digital color encoding is, by definition, the numerical description of color in digital form. For example, in one particular color-encoding scheme, the set of digital values 40, 143, and 173 specifies a particular shade of red (the reason why will be explained later). The fact that color can be digitally encoded implies that it somehow can be measured and quantified.
But color itself is a perception, and perceptions exist only in the mind. How can one even begin to measure and quantify a human perception? Vision begins as light reaches the eyes; thus, a reasonable place to start is with the measurement of that light.
In the color-science courses we often teach, students are asked to list factors they think will affect color. There usually are quite a few responses before someone mentions light sources. But perhaps this should be expected.
It is easy to take light sources, such as the sun and various types of artificial lighting, for granted. Yet unless there is a source of light, there is nothing to see. In everyday language we speak of “seeing” objects, but of course it is not the objects themselves that we see. What we see is light that has been reflected from or transmitted through the objects. We “prove” this in the classroom by switching off all the room lights and asking if anyone can see anything at all! This usually gets a laugh (and most often results in one or two students taking a quick nap)!
Because color begins with light, the colors ...