The easiest way to change eye color in photoshop

Open your photo by selecting File - > Open .Now browse for your file, select it and press "Open".
An easier way to do this, is by simply dragging the photo into your Photoshop canvas.

Here's the photo I've used:

Same as in the previous tutorial, press Q, in order to activate the "Edit in Quick Mask mode" option.
Choose a hard round 19px brush and paint the whole iris area, leaving the black spot in the middle alone.
This is how your picture should look like:
Next thing to do is going to Image  -> Adjustments -> Hue Saturation [or simply pressing Ctrl+U].
Check the colorize box, and play around with the values until you will get the color you need.
These are the values I've used:

Next step: Go to Image -> Adjustments ->Curves... [Ctrl M]. A pop-up window will show up. Also play around with the values until you get the desired shade.
This is my final result:

This is it folks. Hope this is useful..and goodluck..:-)