The simplest way to check for color accuracy is by visual comparison. If your system is well calibrated, you can view the printed output under standard viewing and lighting conditions. This method is easy, but highly inaccurate. This system is widely in use in the color reproduction industry for its ablility to measure color in a 3-dimensional fashion. This is believed to be a more precise way to measure color frequencies.
Color is measured by measured by measuring the reflectance of different wavelengths.
There are several kinds of instruments in use to measure color with varying degrees of accuracy and emphasis. A spectrophotometer is one of the more sophisticated instruments. Many spectrophotometers have computers that display results in the CIE and other formats. Anouther instrument for measuring reflectance is a Colorimeter. Many Colorimeters can also display values based on the CIE System.