This in my opinion is the best easiest and simplest way to edit hair color in photoshop watch an learn young padawans
Instructions are as follows,
Create new adjustments layer> choose color you wish
Set Layer blend to Overlay
Fill adjustments layer with black to mask everything> Paint back in color with white and your paintbrush.
Double click layer to change the color to your choosing
Most importantly have fun!
Check out the others in the series
Editing Hair Color in Photoshop with Paint Layer. [link]
Edit Hair Color in Photoshop with Hue and Saturation [link]
If you like it fave it, if you've suggestions for videos let me know