Most TN panels are very fast switching but only able to produce 262k colors, using dithering to display the 16,7M delivered by the PC. The issue might be important if you're a photographer.
But always keep in mind that the end product - the print - might show much less than even 10k distinguishable colors, so this issue might be overplayed by some geeks.
I suggest reading these articles and comments.
at TFTcentral & Photo.net