Low response time is going to help reduce blur. This is especially important when try to pick out targets on the move. 1 to 2 ms is ideal for gaming.
High refresh rate monitors are good for reducing noticeable tearing. This is key with first-person shooters. Because you're always turning to pick out targets. Tearing is quite noticeable on 60Hz monitors and definitely takes away from the gaming experience. You can turn on V-sync to eliminate tearing on any monitor, but this introduces input lag (the difference between you clicking the mouse and seeing the effect of the click on screen). The best option is to run at higher framerates so it's less noticeable. 96Hz and above seems to be the point by which tearing becomes perceivably non-existent so anything above that refresh rate is ideal for gaming. To add to this, if you have a newer Nvidia graphics card, you can take advantage of G-sync which eliminates input lag, blur, and tearing. Monitors fully supporting G-sync out of the box should be available within the next few months.
Contrast is really important when it comes to gaming. You want to be able to see the enemy lurking in the shadows. A monitor with poor contrast will just show no difference between objects in shadows. Beware the low-end (and really many that are pretty expensive) IPS monitor with poor contrasts. On these monitors the enemy is not discernible in shadows.
Color is important, but just about any monitor is going to provide the colors necessary to game.
Another thing you should consider in a triple monitor setup is the bezel size. You want things to look as seamless as possible between the monitors so the smallest you can find, the better.
If I were to buy today, I'd grad any of the 120Hz or 144Hz monitors available from Asus, BenQ, or Acer (if you can still find them).
This Asus is not a 27", but rather a 24" that has some great reviews and would be great for a triple monitor gaming setup:
http://www.newegg.com/Product/Product.aspx?Item=N82E16824236313
Last, you are definitely going to need 2 or 3 high-powered video cards (ie 780s or 780 TIs) to stay consistently between 60 and 90 fps across 3 monitors.