This is like watching some preschoolers argue whether the rainbow has 4 or 5 or 7 colors. The arguments do not make sense at all because they are actually some form of opinion.
The author presents a four-color primary set. It clearly has its roots in Helmholtz's color physiology, but I confess I don't quite understand how it would be used. For me, I would miss the important blue/orange pairing.
So the author is correct that there are four opponent colors, but not correct that they can all be arranged on a wheel so easily.
Color spaces are three dimensional geometries, attempts to reduce them to two dimensions are always wrong just like every 2D map projection creates distortions.
Yellow is not lighter than blue, though I can understand why you say this.
In the hue, saturation and lightness (hsl) understanding of color, hue terms such as Blue/yellow and lightness terms such as light/dark are separate entities.
It is perfectly possible to have a blue and yellow of the same lightness value, but the yellow would be more dull. More dull = less pure = less saturated. The peak saturation to lightness of different hues is not consistent. Yellow is most yellow (ie most saturate/pure) when it is quite light. Conversly the peak saturationn of green or blue is in the dark range.
As you rightfully state, One key issue with the color wheel is that it is two dimensional. There does not exist a remotely complete color model that does not recognize at least three dimensions.
I am not dissing the utility of the color wheel, but it has application only to the ordering of hues.
If our eyes somehow detected the exact wavelength of light directly then, yes, we would perceive a continuum of colours and it would be totally arbitrary how you divide it up.
But we don't. As the article says, we have a discrete set of cone types that divide our perception of colours up into clusters (albeit overlapping and fuzzy). For that reason, for most people with normal vision, a rainbow appears to have 6 main colours.
The 6 colors of the rainbow are arbitrary and cultural (I've always learned there are 7). There's no physiological reason we say orange is a color but dark orange isn't. We perceive more than 7 colors.
Why seven colors? Because Isaac Newton felt it must be 7 due to it being a more mystical number, so he shoved indigo in there.
> The question of whether everyone sees seven colours in a rainbow is related to the idea of linguistic relativity. Suggestions have been made that there is universality in the way that a rainbow is perceived. However, more recent research suggests that the number of distinct colours observed and what these are called depend on the language that one uses, with people whose language has fewer colour words seeing fewer discrete colour bands.
While we're here, one of my favorite unsong quotes, at roughly the same level of woo:
> Then there was light.
>
> Beautiful, multicolored light, ten colors, the seven colors of the earthly rainbow and the three extra colors you only get in Heaven. Ten colors corresponding to the ten sephirot and the ten fingers and the Ten Commandments and the ten digits of the number system and the ten pip cards of the Tarot and all the other tens in all the correspondences of the world.