Photoshopuniverse will show you how to change a person's hair color in PhotoShop. You can achieve this by using hue and saturation adjustment layers and set to colorize. Set the saturation to about 50%. Go back to the background layer and select the color range select parts of the hair color, select the parts of the hair you want to change and with the eye dropper click it. Once the selection is made invert the selection the color will change. You can now change the hue to make it what you want.