This wheel explores a heuristic about the line of purples
Purple, unlike Violet, is a composite color, composed of red and blue. In humans, there are 3 cones, red, green, and blue. Pixel lighting exploits this fact to generate a full gamut of human perceptory colors.
A common point of confusion is the color wheel. Electromagnetic radiation (of which visible light is one manifestation) doesn't actually loop back in on itself. It actually continues in both directions, to 0ƒ from red and to ∞ƒ from violet.
For example, different species have different lines of purple, i.e. Bee Purple which is a combination of yellow and ultraviolet light in the human spectrum.
It is of particular interest that purple is perceived as a bridge of a discontinuity in perception since it is the composite signal of the low frequency cone (red) and the high frequency cone (blue). Composites with the mid frequency cone, green, are percieved as a linear spectrum since they correspond with a spectral frequency; whereas purple fabricates a relationship between the highest and the lowest receptors where there is none. In that regard, the purple space of perception can be treated as an anti-color of a spectral analog that spans equivalent extrema of frequencies: a parallel rainbow unto itself.
The specific interest of this exploration is in the temperature of color, which is a qualitative measurement. A color can only be "warm" or "cool" relative to another one. For example, painters have historically noted that a cold red (crimson) is actually cooler than a warm orange. In general, the warmest color is red, and the coolest color is blue. Since purple is the composite of both, it stands to reason that shades of purple can range from the warmest to the cooles extremes relative to other colors.
- It might be relevant to note that the rods (b & w receptors) are actually most sensitive to spectral yellow-green light, and hence wash out frequencies in that domain. This is why there are no dark yellows, and no green stars. Broad-spectrum green-centered radiation is percieved as white by the human eye given biased signal amplification since there are so many more rods than cones.
The author believes from many years of observation as an artist, that there exists an analog in purple for every color on the spectral rainbow. As such every temperature relationship on the natural rainbow can be substituted in whole or in part with a corresponding shade of purple.
The content of this project itself is licensed under the Creative Commons Attribution 3.0 license, and the underlying source code used to format and display that content is licensed under the MIT license.