All those sayign 24-bit is more than enough obviously haven't spent much time working with video and graphics ;) Look up "mach banding". Its amazing just how bad the mach band effect is ... suspect it will still be slightly visible with 30-bit colour ...

There was a slight term misuse in the article, which also relates to why having more than 16 million colors makes sense: Dynamic range. 24 bits vs. 30 bits has nothing to do with resolution, but instead bit depth.

Now, while the eye can't necessarily distinguish all those colors all at once, our eyes adapt to different brightness conditions very well. With 24 bit color having a naturally bright sky and really deep shadows at the same time is impossible. If you jack up the contrast so much that both have the correct amount of brightness the limits of 24 bit color start to show.

Google HDR imaging or check out this wikipedia article for details:
http://en.wikipedia.org/wiki/High_dynamic_range_imaging

You may ask why so many colors. Well it really doesn't pay off if you make a screen that can show 1 billion colors on the same gamut of the 16,7 million colors screen. The fact is that humans can perceive much more colors than the ones present on the sRGB or even Adobe RGB gamut.
The human vision can perceive at least twice the gamut displayed on current monitors. So there are colors we see in the real world that cannot be reproduced.
And that's why a monitor that can display more colors matter (as long as those extra colors are beyond the current 8 bits RGB gamut). The catch is that you only can reproduce it if your camera can catch it. So the majority of digital cameras that capture pictures and save them as JPEG won't benefit a bit. On the other side cameras that save pictures as RAW files will get a boost on screen.

Hope it helped understanding it!

@MH: Set your monitor to 0/255, 0/255, 0/255 (black). Now set it to 0, 0, 1/255 (i.e., one shade lighter of blue). Notice the change?

Keep increasing the total number of colors/shades until you no longer notice the change from any shade to its adjacent shade. The total number will be larger than 2^24.

In other words, I think your premise ("the eye can distinguish a million") is somehow wrong, or just overgeneralizing.

If you put a 0,0,0 pixel and a 0,0,1 pixel next to one another on a field of 128,128,128, the eye won't be able to distinguish them. If you fill half your screen with 0,0,0 and the other half with 0,0,1, you'll see the line.

If you put a 1" 0,0,0 square in the left half of your screen and a 1" 0,0,1 square on the right half--again on a 128,128,128 field--your eye won't be able to distinguish them. Now animate them back and forth from 0,0,0 and 0,0,1 and you'll be able to tell.

And how many colors can you fit into a 1920x1080 space with 1 color per pixel? Not a billion, that's for damn sure.

Well MH, make a ramp of one primary colour across a large display, say green, there will be 256 gradations, your eye can easily see the banding, because there's only 256 'colours' of green (and the other primaries).
That's why 24 bit is too little, and who the hell told you the human eye can't see more than million anyway? That's poppycock.
Not to mention grayscales, there the eye is even better and the 256 values is really a bit low.

Well, try to compare 6-bit panel with 16.2 million and 8-bit panel with 16.7 million. Unless you are color vision challenged, you will see a huge difference (rainbow effect anyone?).
And now check the same/similar content on 10-bit LCD HDTV (Samsung 4681?) Do you see the difference?

To summarize: only billion colors and above more or less correctly reproduce colors, the rest is just an immitation.

Pfft, wish they used that money on making OLED displays better.

I remember technical articles back in the early 80s touting how digital TVs featuring an impressive 256 colours were the way of the future,

I can hardly wait for some lawyer with too much time on his hands to sit and count "only" 999,999,936 colors. Clearly, HP is attempting to mislead the buying public, and their claim of "a billion colors" is clearly a marketing getting ahead of technology. He will then demand $1-billion US for pain and anguish at not having 333,333,330 discrete shades of blue.

I can't figure out why you should need more colours as the eye supposedly only can distinguish a million of them. That is roughly 20-bit colour. 24-bit comes from the mathematical convience of 8-bits for each colour component hence RGB 2^8 * 2^8 * 2^8 = 16.7 million. Why need a billion? I'm sure some Photoshop guru will tell me.