ELI5. Why mixing colours give us other colours. Like what’s the science behind?
In: Chemistry
That’s how our eyes work. We have three types of cone cells in our eyes, “red”, “green” and “blue”. Each of them [reacts to different wavelengths](https://www.unm.edu/~toolson/human_cone_action_spectra.gif) of light differently: they produce a strong signal when they “see” light corresponding to their colour but the signal gets weaker if the wavelength differs from the peak point.
The combination of these three responses is what we call a colour. But we can combine light in different ways to make our cells perceive it as something else: for example, a mix of red and green light will be seen as yellow since it produces a stong reaction from red and green cells but weak reaction from blue cells, just like “normal” yellow light does. That’s how screens work.
Mixing paint works in a kinda similar but inverted way. Paint doesn’t produce a coloured light, it absorbs part of light falling on it. White light contains the entire spectre and, for example, a yellow paint can absorb parts of it that are far away from the yellow colour leaving only yellow part to be reflected in your eyes. When you mix paints, you take away different parts of the spectre, leaving a combined colour.
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