This is something that i've been curious about for a while now, and when we started learning about light in physics a few weeks ago I decided to experiment to learn more about how the computer manages color. I've always known that white light is made up of red, green, and blue light, and that the intermediates are cyan, magenta, and yellow. What is most important to notice is that there's no way to produce black using r,g,b, light. Black is the absence of r,g, and b, much like white is the absence of c,m, and y in CMYK mode. Something else important to know is that there's simply no way to produce some of the brightest values of r,g,and b, using CMYK inks. In theory you should be able to produce the entire spectrum of colors using C,M, andY, but in reality you need to add black for the darker colors. the following picture is a pretty common image used to describe the difference. it shoes the entire range of human color perception, and what can be reproduced using RGB and CMYK Colors.
So the moral of this story, as far as i've been able to figure out, is to reduce your screen brightness to about 70%, to have more realistic expectations of what you can get when you print something that you were designing in an RGB colorspace, Design in a CMYK colorspace if your destination is print, and pay attention when you pick a color and photoshop gives you that little exclamation point saying that the color you picked is "out of gamut."Because as you can see, more than half of the colors that we can see are not able to be reproduced by printing inks. Sorry for the rant, but writing this down really helped me learn what i'm talking about, and in the non academic world, this stuff is really important.
