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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So I can’t give you a good explanation of why a certain wavelength comes from a surface of a certain substance/material, but I can tell you a bit about the light itself and how your eyes deal with it ^^and ^^rant ^^a ^^lot ^^about ^^color ^^theory.
So first off, your eyes have special sensitive cells called photoreceptors which respond to light. There are two kinds of photoreceptors: rods and cones. Rods are not color-specific and are more sensitive to low levels of light than cones, and this is why in really low-light situations it’s hard to distinguish colors. Cones are what you’re more interested in, and there are three kinds. Each kind detects a range of light, peaking in red, green, or blue depending on which type of cone cell. [Here’s a picture of the wavelengths each cone is sensitive to](https://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Cone-fundamentals-with-srgb-spectrum.svg/810px-Cone-fundamentals-with-srgb-spectrum.svg.png).
So now we have three primary colors we can work with and mix together. Different amounts of red, green, and blue can appear as the different colors on the spectrum. This is how the screen you’re looking at now works: lots of little glowing dots in red, green, and blue vary in brightness to appear as all the colors in the RGB color space. *It should be noted that they can’t produce all the colors your eyes can see*, but it’s complete enough for realistic-looking photos and videos. White light contains all the colors, so when a pixel on your phone looks white, each red, green, and blue part is emitting at 100%. Likewise, black is RGB(0,0,0) – ideally this would be zero light emitted, but your screen still glows a bit. We’ll just say it’s zero.
This is what we call the “additive” color model, because we’re adding different color elements together. There’s also the *subtractive* color model, which is more useful for describing mixing pigments, paints, or other things that *reflect* instead of *emit* light.
Pigment mixing, or “subtractive” color, is the same thing as the additive model, but in reverse: the things like your house, clothes, and blood actually *absorb* some wavelengths of light. You know how your black shirt gets hotter than your white shirt in the sun? It’s absorbing more light. Remember how on your screen, black is RGB(0,0,0)? Well it’s kinda like that. All the wavelengths (ok not all but for our purposes “all”) are being absorbed, and none reflected, so your eye basically gets RGB (0,0,0) from your black shirt. Whereas the white shirt reflects all the wavelengths (ok not all but, again, ya know…) and your eye receives RGB(100%,100%,100%).
So when we’re mixing paints, pigments, etc, we want to know how much of each to use, right? Let’s use a printer as an example. It uses four colors of ink. Cyan, magenta, yellow, and black.
This is where I think it gets really cool.
If we consider cyan, magenta, yellow, and black the “primaries” in subtractive color mixing, *they’re actually the secondaries in RGB!* Check it out. Mixing 100% red and 100% blue in the RGB model makes magenta, red and green gives you yellow, and blue and green gives you cyan.
[Seriously, check it out.](https://www.csfieldguide.org.nz/en/interactives/rgb-mixer/) I know it sounds weird that red and green give you yellow, but that’s probably because you’re used to the red-yellow-blue model of the color wheel. I’ll get to that.
So just like before, the *additive* model and the *subtractive* model are the reverse of each other! The primaries in one are the secondaries in the other. When your printer wants to print red, it’ll use yellow and magenta. Because we’re *subtracting* light instead of adding it. This might not be very intuitive but if you think about it, it kinda does make sense in a really cool way (at least I think so but I’m a nerd so 🤷🏻♂️). Think about it: Which color do yellow and magenta have in common in the other model? Red!
[Again, check it out.](https://www.w3schools.com/colors/colors_cmyk.asp)
More pigment makes things darker. Subtractive. Technically, mixing cyan, magenta, and yellow will give you black, but your printer adds black for more defined dark colors, and to save ink (you’d use a lot of ink printing black text if you’re mixing ALL the colors).
So what’s the deal with the color wheel? I grew up thinking that the primary colors were red, yellow and blue. In these new models, that doesn’t make sense, right? Well, if you squint real hard, a red-yellow-blue palette kinda looks a bit like a magenta-yellow-cyan palette. Kinda. I’m comparing these two because they’re both subtractive. When you’re working with red, yellow, and blue paint, you can make a lot of the colors you can with cmyk. Probably enough for most people. And of course, red, yellow, and blue give us the color wheel we’re all familiar with – Red, orange, yellow, green, blue, purple.
There’s still a problem here. So far I’ve been assuming we’re mixing colors on a white surface. Since subtractive colors are, well, subtractive, we’re assuming we’re starting with all the colors (white) and subtracting from there. If we’re starting with a dark surface, we’re not going to get any brighter colors than the pigments we’re working with. you could make gray with cyan, magenta, and yellow, but you’re not getting white. Simple solution: white pigment. White paint is almost like “cheating” in subtractive color. You’re essentially subtracting your subtraction. Which is just adding with extra steps.
Anyway I think I’ve covered most of it. I’ve probably forgotten something or worded something poorly or maybe gotten something technically or completely wrong; if that’s the case I invite corrections in the interest of giving OP the most correct answer we can. I also don’t feel like going back through this and editing it right now so I’m sorry if this is kind of a stream-of-consciousness wall of text or presented poorly (grammar, punctuation, spelling, etc included).
[EDIT: There’s more. There actually are more color models, like HSL and HSV. We’ll cover that next semester when you take the 200 level course]
OP if you still have any questions, lay it on me and I’ll try to shed some light on it.
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