I'm trying to describe hue (as in hue-saturation-value) in the context of red-green-blue pixel value: specifically, how the axis for hue has no beginning or end, nor objective ordinality like a set of red, green, and blue pixel values would have.
I'm posting this on Maths.SE because this seems like an analog of spherical coordinate systems. In mathematics, one might categorize an axis like azimuth separately from radius and the typical Cartesian x, y, and z.
Is there a word for such an axis, where moving some distance D along the axis can bring you to the same point -- as opposed to axes where moving D always brings you to a new value, or to a forbidden value because the axis has some limit?