Why do the colours I’ve set up on screen end up looking different on the final print?
Here’s where it gets tricky. Hopefully by now you would understand that the way a monitor produces colour and the way a printing press produces colour are two very different things. The colour gamut (total range of colours available in a particular colour space) of an RGB monitor as opposed to a four colour process print (CMYK) are very different, however they do overlap (see illustration below). The spectrum of colors seen by the human eye is wider than the gamut available in any color model. So some colours will print out in similar hues to what you see on your screen while others will not. Either way it is important to remember that the colours on your screen will always look brighter and more vibrant than they will on a four colour process print. The reason for this is that the light producing the colour on your monitor comes from beams of light straight to your eye, whereas colour from a print is seen by light reflecting off the print (some of the light is absorbed) and then trave
