[nkrisc]

The lines are arbitrary, but it may still be useful to draw them for some applications.

It’s a rainbow all the way back to the first tetrapod (and beyond). But clearly we are not fish, so somewhere in that spectrum there is a useful distinction to be made, a line to be drawn. Of course, the closer you get to finding that line, the faster it vanishes. It’s equally futile to say that we are indistinct from fish because there is no clear and decisive separator.

[lazide]

Yup, same with drawing lines on a rainbow.

The concept (and definition) of red, orange, etc. is important and useful. A great many things would be impossible without it frankly. [https://en.m.wikipedia.org/wiki/Spectroscopy]

Applying it in real life in some situations sometimes has a fractal like quality. Like measuring a shoreline.