Cheap monitors are generally not good if you want color accuracy because they use 6-bit color technology as opposed to 8-bit color technology. Basically a 6-bit LCD monitor can only produce 64 shades of Red, Green and Blue which means only 256k of actual colors can be produced. An 8-bit LCD monitor can create 256 shades of R,G,B which means an actual 16.7m of colors can be produced.
6-bit LCD monitors must use A-FRC (Advanced Frame Rate Control) to blend up to around 16m colors. It is known as temporal dithering. The pixels flicker between two color very rapid to blend a 3rd color that the LCD panel cannot normally produce. For example, the pixels would flicker between red and blue to create purple. The results are inaccurate colors and color banding issues when gradients are concerned as well as possible pixelation issues in some rare instances.
Basically all cheap monitors use 6-bit panels. All TN panels are 6-bit. Nearly all e-IPS panels are 6-bit with maybe two panel models that are actually 8-bit. More expensive monitors like the Dell U2410 use an 8-bit IPS or VA panel. The Dell U2311H uses a 6-bit e-IPS panel. It is still better than a monitor that uses a TN panel, but generally not ideal if color accuracy is important.
The NEC EA231WMi maybe something that is more appropriate. It too uses an e-IPS panel, but based on reviews from people who compared the Dell U2311H and the NEC side by side, the NEC seems to have less or no color banding issues. This indicates that the NEC EA231WMi may actually have an 8-bit e-IPS panel.
Here are a few of reviews:
http://www.xbitlabs.com/articles/monitors/display/nec-ms-ea231wmi.html
http://www.tftcentral.co.uk/reviews/nec_ea231wmi.htm
http://www.flatpanelshd.com/review.php?subaction=showfull&id=1265977876
Those reviews are relatively old so they will probably say the NEC uses an 8-bit e-IPS panel. Even reviews of the Dell U2311h will probably say it uses an 8-bit e-IPS panel. That was a logical assumption at the time since all IPS panels that were manufactured before the e-IPS panel were 8-bit panels.
It was not revealed until this year (February 2011) that nearly all e-IPS panel models were in fact 6-bit panels.