Heathrowe.com has posted 3 easy steps to replace eye color with photoshop CS/CS2:
“Switch back to your original target image. (Duplicate original image layer before proceeding)
A. Activate the ‘Color Replacement Tool (B)’.
B. Then up on the Options Bar, select a brush preset and ensure your ‘mode’ is set to ‘Color’, as captured below.
C. Then brush over the old eye with the new foreground swatch color.”
Here’s the before and after image: