: if colour is a spectrum going red thru purple then why do we have colours like magenta or pink, which seemingly connect purple back to red?
In: Physics
Because our eyes and brain don’t directly detect the frequency/colour of light. Light is a continuous spectrum of wavelengths and our eyes have 3 types of cells (cone cells) which are responsive to different ranges of these wavelengths. These roughly correspond to red, green and blue light.
When the red cone is triggered we see red, when the blue cone is triggered we see blue. When all 3 are triggered equally we see white. If we send light of a wavelength between these regions then more than one gets activated. For example yellow light has a wavelength between red and green, so it triggers both cones and we see yellow. However we could achieve the same thing by using just red and green light to create the same response. This is why screens and cameras only need red, green and blue pixels to display all of the colours that a human can see.
Now consider what happens when we receive both blue and red light, both of the cones are triggered and we see magenta/purple. This means if you take the spectrum of light and imagine connecting it at both ends, the mid ground between red and blue will be purple.
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