I noted that most LCD monitors, up to 24inch support only 16.7mil colors. However, when going to LCDTV with 10bit panel (like philips 32PFL5403S), it can display billions of colors - I am not sure if such additional depth is significant for a 22 inch or 24 inch LCD monitor (ie richness or realism). Is it that most (up to 24inch) LCD monitor (for PC) are not 10bit - if so, there must be a reason for this I assume.
I only found 10bit panel for 32 inch (cant seem to find for 24 or 22 inch), and for a desktop computer 32 inch is quite bulky isnt?
10 bit isn't really necessary, though there are a few panels that you can get that support it. 8 bit is really all you need, though make sure that your panel is a true 8 bit if you care about color accuracy. Most TN panels (used in cheap monitors) really only support 6 bit color, and then use techniques like dithering to imitate true 8 bit support. Good 24" panels and bigger tend to use the S-PVA and S-IPS panels that support true 8 bit though, allowing for significantly better color. There are a couple of 24" panels that support 10 bit, but they are extremely expensive, and not worth it unless you do graphic design or similar work that requires extremely good color reproduction.
It is due to the usage of an internal color LUT (look up table). The panel itself is still 8-bit (unless they are starting to hook up a LUT to a 6-bit panel; which is a real waste of money).
Typical 8-bit displays can generally produce up to 16.7m colors, but through the use of a LUT extra precision can be obtained. This does add a little bit of time to input lag since colors are checked against the LUT to determine if there is a more precise color to display.
Due to the phyiscal limitation of the actual number pixels and HDTV can only display roughly a max of 2.05m colors at any given time.