Your monitor and television are made up of RGB, or red, green and blue combinations, and they are responsible for all of the colors you see on your screen. They are referred to as primary additive colors because they are light projected. In other words, there is no light or white present until those colors are turned on, like a flashlight. To prove this, turn off your TV or computer screen and tell me what you see.
CMYK - cyan, magenta, yellow and key (black) are the colors used in printing. Combined, they are referred to as 4 color process. They are known as primary subtractive colors because they are added to the (generally) white paper they are printed on. In other words, you are subtracting white by printing over it. Cyan, magenta and yellow are capable of printing all colors but true black. The black you get looks very washed out, so black is added. It is also used because it minimizes CMY ink usage, cutting printing production costs.
Next is a sample breakdown of a 4 color photo of the Grand Tetons in CMYK separations utilized for printing. The final photo shows how it would print.
Now that you understand primary additive and subtractive colors, you can tinker around with RGB or CMYK combinations to make your own. The sky's the limit.
As I got more involved in color printing and moved away from the mostly stark world of newspapers and black & white, I played around a bit. Years earlier, I had come up with velvis and reincornation as funny words sometimes referred to as portmanteaus, so it was inevitable that I would create something visual since I was in the graphic design profession. In light of this, I came up with a new color and called it vagenta. I'll let you figure it out.