: What are the true complementary colors and their values ? Being a webdesigner I learned that Green= 00FF00 Blue= 0000FF Red= FF0000 Yellow=FFFF00 Correct ? And color theory says that Red is

@Speyer780

I think another basic, physiological way to visualize a complimentary color is the following. In a room that is totally dark, shine a bright spotlight onto a swatch of colored paper. Stare for a while at the color and while you are still staring, shut the light off quickly. The complimentary color will appear and remain for a short while.

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@Hamm6457569

There is a lot of confusion over various color models because the physics of color and light and the biology of the eye were not well understood when the predominant theories emerged in the arts. The red, yellow, blue model is a holdover from years of trial and error with imperfect (and hard to find/expensive) pigments that is useful to a point, but is not entirely accurate.

You can use any three colors to define what's called a color gamut, a subset of all possible colors (http://en.wikipedia.org/wiki/Gamut). These colors make up a triangle with each one marking out a point. You can then combine these colors to make all possible colors inside the triangle, but you can never make a color that falls outside the triangle, so, in whatever medium you're working in, you want to choose colors that are as far apart as possible to make the widest gamut. Whatever three colors you use are called the primary colors of your color system.

When you're working with light, the colors that make the widest gamut are red, green and blue, so these are called the primary colors of light. This system is called additive color because you start with black (darkness) and add different amounts of red, green and blue to make the various colors. When you have equal parts of all three, you get white. (http://en.wikipedia.org/wiki/Additive_color)

If you're working with ink or dyes or paint, the widest gamut uses cyan, magenta and yellow. This system is called subtractive color because you start with white (say, a piece of paper that reflects all light evenly) and the pigments you add absorb light, keeping some color from reflecting off the paper. So a cyan ink really just absorbs red, leaving the green and blue light to reflect. When you have equal amounts of all three, you get black. (The reason for k - black - in the cmyk system is that the inks are imperfect - don't absorb all of the light they should - and adding a black ink makes the darks darker.) (http://en.wikipedia.org/wiki/Subtractive_color)

Turns out that because the subtractive system absorbs the light from the additive system, the primary colors of light are the compliments of the primary colors of ink and vice versa.

On the web, you're using light (generated from the computer monitor) so you should think of red (#ff0000), green (#00ff00) and blue (#0000ff) as the primary colors and cyan (#00ffff), magenta (#ff00ff) and yellow (#ffff00) as the complimentary colors.

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@Lengel450

Ok I'm answering myself:

For documents to be displayed by a light system such as screens, the RGB color model should be used. It tells us what are the complementary colors for the three primary colors:
Cyan for Red,
Magenta for Green,
Yellow for Blue.

Now if you want a tool that tells you which color is the complement of the color you picked, you first need to verify that whatever tool you chose, its color wheel gives the same result as the RGB model. One such tool for Mac is Painter's Picker (a plugin for Apple's Color Picker). Color schemer tools however usually give false results. Basically, any tool that can invert a color can tell you the complementary color (most complex image editing softwares have such feature, it's also built in Mac OS X Universal Access preferences).

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@Kevin459

Colour scheme generators such as Kuler don't give you the exact values because they are focused on giving you a scheme and they are design based. A colour scheme of the exact opposites would look rather garish and over the top. Kuler is a tool to allow you to contrast colours whilst still keeping the scheme looking nice.

Summary: If you want a true colour conversion tool, don't use a colour scheme generator, because they are focused on getting things to look nice for you, not to give you exact measurements.

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@Caterina889

I think you should be using RGB complements (in the "Light" answer). The RYB complements were from an era when people didn't know of light's primary colors being RGB. RGB complements look nicer, in my opinion. Here what some random dude named Lira had to say:


RYB is the traditional colour wheel,
used by artists. Sir Isaac Newton was
the first one to come up with this
sort of thing. And it was kind of fun.
Here, take a look:



Recognise it? It's the colour wheel
Jason Beaird used in his "Color for
Coders" article. Remember that, when
we're in kindergarten and stuff, we're
taught stuff like "Yellow plus Red
equals Orange"? It all comes from this
colour wheel, whose primary colours
are red, yellow and blue (they're
touching the darker triangle, poiting
upwards). Warm colours occupy half of
the space and cold colours the other
half. That's like a colour Yin Yang.
Almost too perfect to be true.

Indeed, it was too perfect to be true.

Scientists then find out that
biologically, it doesn't really work
that way. Anyway, after studying,
researching, analysing, chopping and
cooking colours, we ended up having
the RGB colour model, ubiquitously
present in stuff like computer
monitors, TV's and so on.

As you might be assuming, the colour
wheels are a bit different. The
opposite of "red" in the RYB colour
wheel is "green", whereas the opposite
of "red" in the RGB colour wheel is
cyan - you can test the latter by
staring at something red (focus, try
not to blink) and then looking at a
white surfice: the afterimage is cyan.
Here's an example:

faculty.washington.edu/chudler/after.html
That means you have two different
colour wheels to choose your colours
from. So, which one of them do you
guys prefer?




Light

A trivial definition of a complementary color regarding the RGB color space is as follows: given a color (RR, GG, BB), the complement is (FF - RR, FF - GG, FF - BB), where each component is given in hexadecimal. As an example:

color = (12, 4A, FF)

complement = (FF-12, FF-4A, FF-FF)
= (ED, B5, 00)


Adobe is using a slightly different definition from this "trivial" method of calculating complements. Perhaps it is more appeasing to the eye, or perhaps it aligns more closely with how the human eye works.


EDIT: Looking at this answer a few years later, I have to say that color spaces, monitors, and the human eye work in weird ways. This means that there is no one "correct" way to calculate complements. Your monitor can only display a certain range of colors, and the human eye is sensitive to certain colors more than others. This leads to many valid formulas to calculate complements.



As you can see, there's a fair amount of gap between 460 - 500nm, leading to a different human perception of expected color mixing than what is shown using actual scientific measurements.

I believe there are certain color spaces which allow for linear additive color mixing that matches our expectations...?


Here, I made a small quick web "app": jsfiddle.net/rXsAT/
Looks like someone already made a nicer version.



Pigments

This is a rather complicated subject involving a bit of chemistry, biology, and physics.

Just know that additive color mixing with pigments is fairly different from light.

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