OS X Yosemite: Calibrate your display
The colors on your display can be altered by many factors, such as ambient light, the position and angle of the display, and the age of the display. To accommodate for these alterations, you can adjust your display to show accurate color using Display Calibrator Assistant.
Calibrate your display regularly to ensure accurate color.
Choose Apple menu > System Preferences, click Displays, then click Color.
Display Calibrator Assistant walks you through calibrating your display, then creates a calibrated color profile.
For a more detailed calibration of your display, select the Expert Mode checkbox, which is at the bottom of the introductory text in the assistant.
When the display profile is ready, it’s automatically assigned as your display’s color profile.
Some displays have additional built-in color accuracy and calibration features. For more information, see the documentation that came with your display.