When you set up a new computer or display, the factory settings may be slightly off, giving the computer a slightly washed out look. To get the colors and display to be rich and accurate, I always recommend spending time to calibrate the colors on new monitors, especially when a computer is using multiple monitors (either dual displays on a desktop or an external display attached to a laptop).
Calibrating displays is done so the computer can compensate for differences in hardware, settings, and color-handling technologies in both the display and computer so that colors appear as expected. Without doing this, a red color on one monitor may appear slightly orange on another. By using a calibrated color profile you can correct for inherent variations in the display hardware.
Many manufacturers provide color profiles for their displays, and while they are fairly accurate, they may only be an approximation of the colors or may not be perfect for your specific setup. The accuracy of color profiles depends on a lot more than just the display, and takes into account numerous factors including the type of video card, the operating system, the drivers, and the environmental factors. This is why the supplied color profiles may not necessarily be the best since they may have been created on a PC being used in fluorescent lighting, which may result in incorrect color adjustment for a Mac being used in a basement under incandescent lighting. Therefore, it's best to recreate the color profiles in the conditions where the display is to be used.
There are a variety of approaches for creating ICC color profiles for displays, with the most accurate being the use of a hardware calibrator to measure output levels at various locations on the display to adjust color and gamma curves accordingly. These calibrators are very accurate, but at a cost of between $70 and $600, can also be rather expensive.
The alternative to a hardware solution is to match color intensities to known values using software, and generate intensity response curves. This can be done with the built-in calibrator in Mac OS X, which is a good place to start for most people. Under advanced mode, the calibrator will step you through a series of intensity levels where you will match intermediate color output levels to known values portrayed by interleaved dark and light striped patterns. The interleaved pattern represents the "true" midrange color between the darkest and lightest that the pixel can output for a given intensity level. Matching the intensity to this point for various levels of brightness will give you an intensity response curve for that color, so the color output will remain linear over the full range of output intensities.
Displays have three colors (red, green, and blue) that are all addressed at the same time with the built-in calibrator by lumping them together as levels of gray, for which you then adjust the brightness and color offset values. Doing this for various levels of brightness (five in total for the built-in calibrator) then builds the correction curve for all the display's colors at once.
While the built-in calibrator is accurate enough for most people, its small controls and use of gray scale makes it rather cumbersome and difficult to use. Additionally, the use of grays instead of setting up calibrations for individual colors makes it harder to be sure each color is properly calibrated.
An alternative to the built-in calibrator is the program "SuperCal," which does the same thing as the built-in calibrator but instead offers matching at multiple intensity levels, and matches individual colors instead of lumping them together into a shade of gray. The best feature of SuperCal is that it runs in full-screen mode with large patterns, and also has large controls to make it easy to finely adjust the color matching. The program will run you through a series of intensity matching routines, and does a good job at explaining what needs to be done at each step.
SuperCal is shareware, and has been out since 2003 but has not had much recognition. The main benefit with using SuperCal is being able to adjust the full range of intensities, which lets you tackle the ranges at the lower and upper intensity extents which are not only areas that the built-in calibration overlooks, but also where the intensity responses tend to deviate more noticeably.
TIP: Create multiple ColorSync profiles for the various areas that you use your computer.
Environmental lighting may change how the colors are perceived on your monitor, so it may be helpful (especially for laptop users) to create colorsync profiles for the most common areas you use your computer to ensure they are as accurate as possible.
Additionally, be sure to check your monitor's settings to be sure the color output levels are even. Many times monitors have options to change the relative output of green, red, or blue to make the output warmer or cooler and adjust for lighting, but this will affect your color calibration.