01. Open your file in Photoshop.
02. Click on the “Edit in Quick Mask Mode” button in your toolbar. (It’s the one to the right)
03. Once you click it, your background and foreground colors will change to black and white. Select the brush tool, and set it to the size you are most comfortable with.
04. Start painting over the iris. What you paint will look red.

05. If you paint over other the pupil or other parts that shouldn’t change color, change the foreground color to white to erase the red.
06. After that, change to “Edit in Standard Mode”. (The one to the left)
07. You will see that everything but the eye has a marquee around it. Now go to the top menu and click “Select » Inverse”. Now you should only see your iris selected like shown below.

08. Now go to “Layers » New Adjustment Layer » Hue/Saturation”.

09. On the first dialog box that will appear click “OK”. Then, on the second one, in the Edit Select Box choose different colors to edit your eye color, since every eye has different eye colors the colors you change will depend on the colors you have.
10. I began editing the Reds in my eye.

11. I edited the blues, magentas and red. Editing them, changed my eye color to green, while maintaining a natural look.
12. Finally, I edited the Master Hue/Saturation and left the Lightness in 0.

13. Select “Hue/Saturation Layer” that is above the original picture, edit the other eye so it will have the same adjustments and maintains a natural look as well. To do so, simply paint over the iris with a white brush. If you make a mistake, paint over it with black to correct it.
14. Now you have two natural looking, different colored eyes.