RBG and CMYK are two of the most popular color spaces. Just about everything uses either one of these color modes. A few examples are your computer monitor (RGB) and anything printed from an offset printer (CMYK). There is lots to learn about both of these color modes, but the following is a brief description with some examples.
RGB stands for RED, GREEN, BLUE and is the format for video monitors, projection, web images and most digital photography. Any time you are looking at a computer monitor or a picture taken from a digital camera, you are looking at the RBG color space. The reason for this is RGB produces some of the most vibrant and brightest colors available. CYMK cannot come close to the colors RGB can produce.
RGB is an additive color space. This means you add the red, green and blue light to your black monitor to get all the colors. Here's the basic concept of RBG: the more light you add the more white things get. RGB values are expressed as numbers (0-255) for 256 possible values for each color. Let's take black as an example. You can get black, which is the absence of light, by having the value of each color as zero (R=0, G=0, B=0). Now let's take a look at white. You get white by having the value of each color at 255 (R=255, G=255, B=255). As you see the colors are beeing added to get the color we want. CMYK has a very different approach to getting the colors you want.
CMYK stands for CYAN, MAGENTA, YELLOW, BLACK. The color black is represented by the letter "K". CMYK is a subtractive color model which means you subtract light from a white piece of paper by adding more and more ink. Here's the basic concept of CMYK: the more ink you put on a paper, the blacker it gets. CMYK values are expressed in percentages. For example white would be C=0, M=0, Y=0, K=0, using no ink leaves the paper white. Black is a little trickier in CMYK because there are several ways to make it. For example you can make black with C=0, M=0, Y=0, K=100, as well as C=60, M=40, Y=40, K=100. The difference between the two examples provided is the amount of ink coverage. Different printers have different ideal black settings, they call rich black.
So since we print with CMYK why even use RGB? The truth is, although CMYK is used for printing, it's really not that efficient for other jobs. It's pretty limited in its ability to display all the colors possible that rbg can. In fact, CMYK is only available to print around 60-70% of the colors available in RGB. Many of the most vibrant and brightest colors cannot be reproduced in CMYK.CYMK is the conventional model for conventional offset printing, even though newer improvements in technology are making printing in RGB a bit easier. Some even think the future of printing, with the exception of exact color requirements, is in RBG.