Its a conspiracy by Big Red to profit from infringing on Purple's intellectual property. All the other primary colours are in cahoots. Its time to take down their shadowy cabal.
Looks great mate, no one would notice if they don't know.
Also I think the template in itself is funny in an anti joke kind of way where you expect him to be protesting something but then he's just holding up an empty piece of cardboard really passionately lol.
Red + blue(indigo) = a color not on the chart? but in between the two colors is clearly green!
We perceive purple as an activation of Red and Blue cones in our eyes... The color itself actually doesn't exist as a discrete wavelength and is a collective hallucination of sorts.
In short: Purple doesn't have it's own wavelength. Neither does white, black and the entire gray-scale or any mixing of any colour with the gray-scale and probably more. They're called non spectral colours.
It might be easier to understand when considering other types of waves. At least it is for me. A simple sound can also be described as a wave with a frequency, but if we play two sounds at the same time, we can't say that the sum of the waves has any specific frequency. The frequencies don't add up or multiply or mix as average. The combined sound can only be described as the addition of two frequencies.
In musical terms, purple is not a note, but instead a chord or interval. Red and blue can be individual notes, or they can be mixed as intervals. White is noise and black is silence.
Literally does... There's a number of colors that we perceive that are fictitious. This is well known in color theory. https://grantsonnex.com/why-purple-doesnt-exist/ Don't believe me? That's fine. Listen to an actual artist who's whole job it is to understand colors. There is no "purple" on the light spectrum. And if you're the type to say violet=purple... then here you go! https://jakubmarian.com/difference-between-violet-and-purple/
If we cannot define a color by a wavelength... then it's a color we have to define by how it's perceived. That's not a "true" or "real" color. That doesn't mean it doesn't exist or cannot be perceived, but that it only exists because we perceive it and wouldn't otherwise.
"Brown" is also the same problem. Brown only exists in the context of light and darkness. You cannot just produce "Brown" light. You can produce vary levels of "Dark" orange... and in the context of a dark or light background you'll either see it as orange or brown.
Anthocyanins are responsible for the color and they act as a pH indicator, changing color from bright red in acid to bright blue in basic solutions. Soil acidity could have an impact on their color at harvest, but it also really depends on how you use them. If you put them raw in a salad, they'll probably turn quite red regardless, but it's also quite common to find them as a purple color.