Color Education

Color is generally defined as the characteristic of any object that’s described in terms of hue, lightness, and saturation. In 1666 Sir Isaac Newton, (Mr. Gravity) through experiments with a prism, laid a scientific foundation for understanding color. Newton showed that a prism could break up white light into a range of colors, which he called the spectrum.

Figure 1.1
- Visible Spectrum

Newton noted that the spectrum was continuous, but decided to use seven color names (red, orange, yellow, green, blue, indigo, and violet) by analogy with the seven notes of the musical scale. (Britannica: "color") Although Newton stated that there were seven colors in the spectrum, he realized that colors other than those in the spectral sequence do exist, but noted that:

All the colors in the universe which are made by light, and depend not on the power of imagination, are either the colors of homogeneal lights (i.e., spectral colors), or compounds of these. (Britannica: "color")

There are three categories for color types. First, primary colors consist of red, blue, and yellow. Combinations (or as Newton put it “compounds”) of these fall into the other two categories: secondary colors and tertiary colors (Color Harmony 16).

Color Wheel
Figure 1.2 - Color Wheel 2

Primary Colors
Figure 1.3 - Primary Colors

Secondary Colors
Figure 1.4 - Secondary Colors

Tertiary Colors
Figure 1.5 - Tertiary Colors

Britannica Online notes that there are three attributes that sufficiently distinguish one color from all other perceived colors. First, the hue is that aspect of color usually associated with terms such as red, orange, yellow, and so on. Second, saturation (also known as chroma, or tone) refers to relative purity. When a pure, vivid, strong shade of blue is mixed with a variable amount of white, weaker or paler blues are produced, each having the same hue but a different saturation. Lastly, light of any given combination of hue and saturation can have a variable brightness or intensity, which is dependent on the level of energy present (Britannica: "color").

Chromatic, nonchromatic, and achromatic colors are visible to the human eye. Chromatic colors are the ones defined by Newton (e.g. red, indigo, yellow). Examples of nonchromatic colors are brown, pink, and magenta. Achromatic colors are applied to black, grey, and white. Britannica Online states that according to some reports, humans can distinguish some 10 million colors, all of which derive from two types of light mixture: additive and subtractive. Additive mixture involves the addition of spectral components and subtractive mixture concerns the subtraction (or absorption) of parts of the spectrum (Britannica: "color").

Figure 1.6 - color Mixture

The three additive colors are red, green, and blue. By additively mixing these colors in varying amounts almost all other colors can be produced. Moreover, when the three primary colors are mixed together in equal amounts white is produced.

Subtractive color mixing involves the absorption and selective transmission or reflection of light. This usually happens when mixing colorants like pigments or dyes or when colored filters are used to cover a beam of light (Britannica: "color").

About Light

In the field of physics, color is associated specifically with electromagnetic radiation of a range of wavelengths visible to the human eye. The radiation of these wavelengths comprises that portion of the electromagnetic spectrum also known as the visible spectrum (i.e. light) (Britannica: "color"). Light, a small piece of the electromagnetic spectrum is the only visible form of electromagnetic radiation. Light has common characteristics with both waves and particles. It can be thought of as a stream of minute energy packets radiated at varying frequencies in a wave motion (Britannica: "color"). A wavelength (the distance between corresponding points of two consecutive waves) is often expressed in units of nanometers (or 1 nm = 10^-9 meters). The wavelengths that make up visible light range from about 400 nm at the violet end of the spectrum to 700 nm at the red end. In an interesting side note, the limits of the visible spectrum are not exact for the human race. All humans have different exact upper and lower limits within the spectrum. As wavelengths get shorter the spectrum extends to include ultraviolet and continues through X-rays, gamma rays, and cosmic rays. As wavelengths get longer infrared rays (which can be felt as heat), microwaves, and radio waves are included in the spectrum (Britannica: "color").

The Measurement of Color

The measurement of color is known as colorimetry. It is difficult to describe the color of a specific spectral energy distribution because the eye perceives only a single color for any given energy distribution. So, to measure color it is necessary to express color measurements using a perception-related method. One method is called the tristimulus system. This system is based on visually matching a color under standardized conditions against the three primary colors (red, yellow, and blue). The three results (called tristimulus values) are expressed as X, Y, and Z respectively. Such data can be graphically represented on a chromaticity diagram (see figure 1.7) (Britannica: "color").

Figure 1.7 - Chromaticity Diagram

This diagram is based on the values of x, y, and z (where x = X/(X+Y+Z), y = Y/(X+Y+Z), and z = Z/(X+Y+Z)). Furthermore, because x + y + z = 1, if two values are known, the third can always be calculated and the z value is usually omitted. The x and y values together constitute the chromaticity of a sample (Britannica: "color").