In theory, a given value -- say xff0000 -- and a color profile -- sRGB is the standard for most "consumer" uses e.g. monitors, cameras, etc -- specify an absolu

In theory, a given value -- say xff0000 -- and a color profile -- sRGB is the standard for most "consumer" uses e.g. monitors, cameras, etc -- specify an absolute point in color space. In practice, my monitor's 0xff0000 is going to look different from yours due to differences in manufacture. In LCD monitors it would be the backlight (color and intensity) and filters; in CRT monitors it would be the phosphors and beam strength. It's possible to bring them in line with calibration, but they'll drift again since phosphors and filters change their properties with age and use. It's the same with printing, except that calibration is more effort and expense. Enter Pantone. Pantone inks are pre-mixed so the color is always consistent. What printers do is they print most of the image using the normal four-color process (CYMK) on a "best-effort" basis and then do a separate pass on critical areas using specific Pantone inks that are guaranteed to yield a specific color. The extra process is expensive so spot colors are typically limited to brand-specific colors (e.g. Coca-Cola Red) and other things where precise color reproduction is important.