Select the EyeDropper Tool from the Tool bar as shown below.

Using the Eye dropper first left click on the hair of the person in the photograph and then select another hair color by holding the Alt key.

The first hair color will be set as the Foreground while the second as the Background.

Step 5: Now select the Brushes Option from the Window Menu or by using the shortcut key F5.

Step 6: Now we will make changes in the brushes Dialog Box so that the artificial hair we grow look real.

In the Brush Palette, go to Shape Dynamics as shown, first check the Flip X jitter and Flip Y jitter check boxes (this will make the hair random) and then change the value of Angle Jitter, Roundness Jitter and Minimum Roundness you get a proper effect.

The values that i chose for each of the following are shown below.