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There has not been an attempt to answer the first part of the question (the part in italic) therefore here is a link to the question in biology stackexchange: https://biology.stackexchange.com/questions/85104/how-do-we-see-violet-color
If violet is a higher frequency than blue and red why does a combination of red and blue appear as violet color in an RGB image?
Which leads to my second question, where is pink in all this? Does a pink flower emit a combination of violet and red frequencies?
Pink does not appear in the electromagnetic spectrum. Like white, it is composed of many pure colors, the combination of which we perceive as pink. Why do we perceive a combination of colors as pink? I have no idea; that’s biology.
In a blank Pages document, insert a rectangle and then click on it. One of the colors to show up is pink. Select this color and your rectangle feels with pink. Now open an app like Color Picker - available in the app store - and select a pixel in the colored rectangle and color picker gives you the RGB value of the pixel. In my case, it was 252, 142, 197. Hence the color pink can be produced by 3 photons of the colors red, green and blue. The numbers of each photon scales as the ratio of intensities. So pink can be obtained by 252 red photons, 142 green photons, and 197 blue photons. See the 2 images below. You should be able to google and find the frequencies of red, green and blue. there is probably a single frequency defined for each color. Actually, each color is in a waveband and the central frequency is used for the definition.
Human color vision depends on three photoreceptors in our retina: red, green and blue. The number of photons absorbed by each of these and their ratio determine the color we perceive. For pink the ratio can be found here: https://www.rapidtables.com/web/color/pink-color.html#chart. It is rgb(255,192,203). Any combination of colors that adds up to this set of rob numbers is pink, so many different mixtures of colors are perceived as pink.
Quantum mechanically, the probability of a photon to be absorbed by an r, g or b receptor depends on its frequency. The ratio of the probabilities determines the perceived color of a photon. There are infinitely many spectral compositions of photons that give the same rgb response, for example pink.
