For about a year I've had a secret weapon I've been using in nearly all of my projects: a colorspace based in spherical coordinates called "BCH" which stands for Brightness, Chroma, Hue. It was described by Sergey Bezryadin and Pavel Bourov. There isn't much information available about it online, but these slides explain everything.
Everyday usage is similar to HSV, but BCH has many advantages. It is grounded in real-world light response according to the user's preferred standard white point reference (D65, D50, etc). The color is represented by a vector where the magnitude is the brightness, the inclination is the saturation, and the azimuth is the hue. The motivation behind its development was to have more realistic exposure and contrast adjustment control over low dynamic range images, such as standard JPEGs. I used this capability to great effect when performing Lukidus last year where it drove the realtime color correction of video micrography.
Since the color is a vector, hue is a rotation around 2 * pi. In the video above, the angle of the velocity is mapped to the hue and I modulate independent multipliers for the sine and cosine components of the rotation. These both start at 0, so we only see red, but as I open them up, more colors are introduced, eventually reaching a rainbow pattern (complete rotation), passing through interesting color palettes along the way. I'm really interested in exploring this colorspace further and have some ideas of different mappings that could benefit from it.
Here's a Shadertoy I made with a BCH implementation and comparison to HSV:
https://www.shadertoy.com/view/lsVGz1
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