Finding White Balance
There is no universal white in nature. Our brain identifies a certain color as white depending on the ambient lighting. The windows of houses look yellow to us from the evening twilight. And the evening twilight looks blue if you look out of the window.
So, for your monitor not to look bluish or reddish, you must set up the balance of blue and red depending on the lighting in your room. The process is called color temperature setup.
It may seem trivial, but most of LCD monitors do not offer a color temperature setting as such. They only offer three independent sliders for red, green and blue, suggesting that you select the optimal correlation between them manually.
A calibrator can solve this problem automatically. You just tell it what color temperature you want to have on the screen, and it will measure the current temperature of white, calculate everything and introduce appropriate changes into the graphics card’s settings. Some models, for example the senior versions of ColorVision Spyder, offer a setup mode in which the calibrator helps position the monitor’s RGB sliders manually by showing you the current balance of these colors and prompting you to decrease or increase the level of a specific color to get the desired result.