The ammount of memory requierd to store a RGB depends on the width of the spectra that is to be reproduced. Either four, eight or twelwe bits memory per colour is normal. If eight bits is used it takes three bytes memory per pixel and three Mega Byte memory for a picture of a million pixels.
Since CRT is the most convenient way to present electronic images nowadays, all modern pre-press is based on RGB. Pictures are scanned in RGB with different resolutions of pixels. Also the new digital cameras work with RGB for colorrepresentation.
If the RGB images are to be reprodused on laserwriters or on films for offset prints it is recomended to store the images as EPS-files. If the images are to be stored pixel by pixel for further use on CRT or LCD-devices they ought to be saved in the norms of TIFF. Since the images normally are stored with eight bits for each red, green, and blue for every pixel, and an image consists of milions of pixels, it can be convenient to use JPEGto minimise the memory neededto save the image.
When to reproduce the digital images on print you must convert the images to CMYK colorstandard. The theory of printing color images is to create colours by diferent layers of ink consisting the colors Cyan, Magenta, Yellow and Keycolor(black). It is notable that when using RGB your results are depending on the equipment. Not two monitors are the same in presenting a special color due to age and use, for instance. To avoid any misstakes it is recomended to convert to the CIE colorstandard to equalize the different monitors and scanners on a worksite.