maybe you too wondered why there is written CMYK on printers. If you have printer or you found out what it means you too know that it is abbreviation for: Cyan, Magenta, Yellow (and K which I will tell later).
Those are the colors that you have to fill inside the machine to print you stuff. Sure this is ok, but why do not we use RGB (red, green, blue)? It seems to be used everywhere so why not in printers?
I thought this because I was thinking that from RGB you can get any color, and sure you can, but only in additive process. Such a process happens for example with light, white light is made up of many different parts with different wavelengths that ADD up. So what does mean that something is red(?), well it reflects only red light absorbing the rest. If you put there blue the material will be even more darker because it will reflect only the combination of blue and red. If you combine everything it would not reflect at all, the object would be black.
So what you want to do is to start with lighter colors, those are cyan, magenta and yellow. They too are able to add up to all other colors + lighter than RGB in this subtractive form. Even then colors are not perfect in printers so you can not add up to some, bright red, blue and green wont be displayed very well.
What the “K” stands for? It stands for “Key” which is the color black (it is the KEY thing). While CMY can add up to black, it would not be very pure since the colors can not be clean, it was decided that there will be black added because in most texts black is used. The letter “K” was used because “B” was already used in the RGB model.