You can set the application to control desktop color, or you can make the changes in the graphics card. Aside from specific color calibration tools, most applications don't tinker with desktop color. Nevertheless, if you have a high-end monitor with sophisticated color controls, it may be best to use them. If your display offers no color controls--as happens both with very cheap and with high-end 30-inch monitors--you'll want to enable color setting changes with the Nvidia controls.
AMD splits its desktop color controls into two different panels.
The left panel deals with general color controls, and works even if you have an analog (VGA) connection; the color changes are internal to the card. The panel on the right, listed under digital flat panels, alters the values in the digital output signal sent via DisplayPort, DVI, or HDMI. You also get controls for such variables as color temperature. Setting the color temperature to 6500K (degrees Kelvin) is generally appropriate for video. However, this adjustment changes only the output color temperature to 6500K; you may still need to calibrate your display to achieve accurate color temperature settings.
Using two or more displays can significantly improve productivity. If you just want to configure two displays for independent use as spanned or cloned displays, the Windows display control panel generally produces adequate results.
On the other hand, both AMD and Nvidia offer feature support for multiple displays beyond what Windows does. AMD's Eyefinity lets you locate the Windows 7 start button on either display. If you configure an Eyefinity group, it treats multiple displays as one surface, with a single resolution that combines the span of multiple displays. For example, you can configure two 1920 by 1080 displays to behave like a single 3840 by 1080 monitor.
Nvidia doesn't offer as much flexibility for desktop spanning as AMD. However, Nvidia's control panel makes it easier to create a surround gaming setup, if you want to have stereoscopic 3D gaming over three monitors. The downside? The three displays must be essentially identical, and must have high refresh rates (120Hz or greater.)
Video and video quality
Both AMD and Nvidia offer controls to improve your video viewing experience.