As a general rule, I recommend a monitor with an IPS panel for color fidelity and wide viewing angle, and an LED backlight for long term image stability and low power consumption. There are a lot of monitors on the market that have both, but they vary widely in terms of how well they perform.
PC Hardware Help maintains a regularly updated online list of currently available monitors with IPS panels. I've found it to be a valuable resource when choosing monitors to purchase for my company: http://www.pchardwarehelp.com/guides/s-ips-lcd-list.php
