How does color work. I know how light gets absorbed and reflected depending on the color of the thing, but that does not explain HOW things have color.
Like. I can have a red house, red clothes and my blood is red. But all those things are VERY different things. What properties do all of them have that makes them red? How does my red look red ? Molecules? And we can mix colors too. What specificly is mixed?
What quality in red paint is also present in my blood?
I am not the best at explaining, but what I want to know is what do same colored things have in common that makes us see them as the same color despite being very different kinds of things.
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Light “come from” an object and go into your eye, with various wavelength. The mechanism of how light could “come from” an object vary a lot, depending on the object.
Once light get into your eye, it hit a cone cell, which send a signal to the brain though an optical nerve; each cone cell is given its own optical nerve (note that I’m being deliberately vague about what exactly is this signal, the mechanism is quite complicated). The precise mechanism is something that is pretty deep into biology. But in summary, there are up to 4 possible types of cone cell (but usually 3, and some people have less), which determine how sensitive it is to certain wavelength. The signal sent by each cone cell depends on the wavelength of light it receives and what type of cone it is.
Finally, the brain receives all these signal and interpret them. The precise mechanism for this is still highly mysterious. Unfortunately, part of the difficulty is that how the brain interpret these visual signals depends on tons of additional context, many of which are not visual-based. But as a first order approximation, the brain combine the signals from individual cone cell into aggregate signals that allows color to mix together. Since most human have 3 types of cone cells, there are 3 types of signal, and since cone cells are extremely densely populated and different types are mixed with each other, the brain interpret aggregated signals from many cone cells near each other into a single color.
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Now, let’s go back to the part we understand the most: how light of various wave length can come from an object. There are many mechanism, but 2 most common mechanisms are: reflection and spontaneous emission.
Reflection: light reflected off an object. A lot of the wavelengths are absorbed, or transmitted through. The light you see coming from the object is the remaining light that get reflected.
Spontaneous emission: electrons absorbed energy somehow which raise its energy level, then at some point, it loses energy, producing a photon in the process.
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