Knowing which color palettes to use for what isn't always as cut and dry as you might like. To help you learn how to create beautiful websites and print materials, you first need to start with the differences between CMYK and RGB and what they mean for you.
If you are new to the world of graphic design, you likely have not run into dealing with this difference yet because most programs automatically adjust to accommodate these differences. RGB refers to the red, green and blue colors that are commonly found on projects while CMYK references the cyan, magenta, yellow and black colors.
Black is referred to as K because back in the printing press days they black was referred to as the key plate since it carried out the key functions involved in creating printed materials. Anything you plan on printing should always be in CMYK format, Web creations should use the RGB format. Why you ask?
Large printing presses use plates, each color has it's own distinct plate. Back in the old days the printer would put one color down, allow it to dry and then proceed to the next color until they had made their way through all of the different colors. Modern printing presses still work the same way but now without the drying time.
Sure, you can print in RGB, but it isn't going to come out looking the same as it will with CMYK. RGB colors are additives in that they blend together to create rich, vibrant shades of purple, deep blues, luscious greens and so on. Unfortunately, ink on paper simply cannot emulate what the Web can in terms of creating graphic images that are truly stunning and awe-inspiring.
Anytime you print, the images need to be dulled down to a style that your printer can handle. All of the bold colors you see online will never come out the same when printed. Your computer screen can literally handle millions of colors, which is why the Internet takes advantage of the technology that makes RGB what it is today.
In the event you do try to print in RGB mode, it is important that you understand that your results are going to vary from what you see on your computer screen. Your printer has its own set of colors that it is capable of handling. Unfortunately, it will never be able to keep up with the millions of colors that your computer and the Internet can handle. If you are doing any online design or Web creation, you should always employ the use of RGB color technology.
To change the way your document appears, locate the document color mode settings (usually in the file menu or document settings) and choose which colorspace you prefer. With it being as simple as it is to switch formats, there is no reason why you cannot have the perfect blend of color in both your online and your print advertising. Try experimenting with the two options and see how much of a difference it makes.