Thank you for putting things straight. I did not apply proper scrutiny before posting that article. But there is still a point to the whole “not a real colour”. Because of the specific way purple is perceived by us it can be a tricky colour to capture with our cameras.
Since you mentioned brown: there is a fascinating video by Technology Connections on brown, worth a watch.
Can we be sure that there is a connection between our perception system and what happens in the camera?
The camera’s sensor wells does only register lightness values. The color comes into the picture via the color filter array (CFA). There are some dyes in these filter patches, but as far as I know their spectral distributions are not perfect.
Rather than focusing on the fact that the perception of purple may result from two sets of sensor reading that are on the two different ends of the corresponding visible electromagnetic spectrum, I would think that the important part is that we are at the outskirts of the cone’s sensor range, where signals are weak, and that we may also be in an peripheral range where the dyes of the CFA does not function too well.
Somebody else may have a more complete understanding of this.
Yes, that “Brown video” is well made and explains very good some important aspects of color, including some visually relativistic aspects as well as the cultural one that I hinted to. Very well worth a watch.