CMYK Color Wheel
CMYK stands for Cyan-Magenta-Yellow and Key color (black). These are the primary colors for the translucent ink used in offset lithography (printing). When you subtract all four CMYK colors, you get the white of the paper (no color). That’s why CMYK is called “subtractive color”. After the jump, learn more!
Click on the image below to view a much larger version.
CMYK Color Wheel
The color wheel above shows three colors in addition to the primary colors. In between each pair of primaries is a secondary color: a mix of two primaries. Cyan and magenta make blue. Magenta and yellow make red. Yellow and cyan make green.
I’ve shown a formula for each color. The numbers are the respective percentages of Cyan, Magenta, Yellow and black (K) in each hue. These are the numbers you would put in as the CMYK values in the Color Picker.
Mixing CMYK Color
When you add cyan, magenta, and yellow together, you get black – in theory. In reality, it’s a murky soft black, so printing a rich black requires the addition of black ink, referred to as the Key color. Mixing these four colors together in various ways gives us almost all the colors in the rainbow.
CMYK Venn Diagram
Out of Gamut
Many colors which are visible to the naked eye are not reproducible on a printing press with CMYK. These colors are called “out of gamut”. We can get pretty close, though. Photoshop and Illustrator have commands you can use that bring your colors back into gamut, so that they print a predictable color.
In the Color Picker, look for an icon of a little triangle, with an exclamation point inside, next to the current color: 
If you see that icon, your chosen color will not print in CMYK. Click on the triangle to choose the closest in-gamut color.
CMYK Out of Gamut
Four-Color Process Printing
In four-color offset lithography (also known as process printing), a full-color image is separated into four plates. These plates look somewhat like photo negatives after they are etched. The black areas of the plate hold no ink. Conversely, the lighter the etched area on a plate, the more ink it will hold. There is one plate each for cyan, magenta, yellow, and black.
CMYK Plates and Inks
Plates printed for process printing such as these are not printed with solid ink*. They are actually comprised of patterns of dots we cannot distinguish with the naked eye. Try looking at a magazine ad through a magnifying lens some time. It’ll look something like this:
Dot Pattern
Each of the four plates is printed in a grid of dots. So that the dots are not overlaid exactly on top of each other, the grid for each plate is turned at a different angle. The black grid is at 45°, magenta is at 75°, yellow is at 90°, and cyan is at 105°. When printed together, they form a rosette pattern.
CMYK Rosette
*Solid ink is printed when we use spot colors.
ST Verschoof says
March 16, 2009 at 11:04 amSo what this article tells us is that CMYK has far less colour variants than RGB has? I finally know the difference between CMYK & RGB now. Thank you!
Dawn Pedersen says
March 16, 2009 at 11:54 amYes, that is correct. You are welcome!
Brochure Printing says
March 31, 2009 at 10:32 pmExcellent resource! One should read this as well as the article for RGB. Really highlights the difference between the two. Great job!
georgeina says
May 21, 2009 at 5:54 amSUCH a useful tutorial.
How do you do the Venn diagram in PS? I’ve been trying to find out for ages: I was shown it once but can’t remember how to do it. I need a way to overlay two colours to help me work out what colour I’m going to get when I dye. Clothing, that is 🙂
Here’s hoping you have time to respond!
Dawn Pedersen says
May 21, 2009 at 7:54 amHi Georgina!
That’s a great idea!
I’ll try to put a tutorial for that together today.
Keep in mind that the colors in dyes will sometimes work differently from the colors in light.
Dawn Pedersen says
June 10, 2009 at 8:53 pmHi again, Georgina! I finally made a tutorial on mixing colors in Photoshop as if they were paint. Your mileage may vary.
Anoula says
September 4, 2009 at 4:54 amHi Dawn,
That is the best explanation of CMYK I have found on the web so far.
I have one question though; does this mean that if you have artwork that only requires a CMYK process and use a litho press for this; that you still get a dotty image the same as with digital printing? In which case the image quality is not more solid than digital?
Dawn Pedersen says
September 8, 2009 at 10:04 amI’m not quite sure what you’re asking, but I should clarify that almost everything that is printed on paper uses CMYK and offset lithography. You usually cannot see the spottiness with the naked eye.
Sandeep kansal says
October 3, 2009 at 9:19 amgood pictures
Gary Young says
March 6, 2013 at 1:22 pmHello, this is a fantastic web site. I think what is being asked in the question above regards the printing dot:
“Anoula says:
09/04/2009 at 4:54 am
Hi Dawn,
That is the best explanation of CMYK I have found on the web so far.
I have one question though; does this mean that if you have artwork that only requires a CMYK process and use a litho press for this; that you still get a dotty image the same as with digital printing? In which case the image quality is not more solid than digital?”
I would answer the question this way: there are two different types of dot use or screening. AM screening, which is amplitude modulation and FM screening which is frequency modulation and also known as stochastic screening. The FM or stochastic screening will closely resemble the digital printer result. AM screening is most typically used by printers.
K.Nandhakumar says
June 1, 2015 at 7:09 pmRes. Madam, I am from India, Trichy. As a dtp operarator i know u very well. ur tutorials, articles are good. Thanks. Thanks, Thanks.
I have not enough knowledge in color correction in a rgb image. (Wedding album). Pls let teach me how to color correct and tricks and techs and color relationship between them.
Thanks
K.Nandhakumar says
June 18, 2015 at 7:45 pmRes. Madam,
Already I read ur color wheel article and saved that page. Unfortunately I missed the same.
I need the article which tells about the how RGB and CMYK colors details
Thanks .