Take the eye that needs to be replaced. More specifically, the photo eye…;)
Now select the tool Elliptical Marquee Tool and allocated to the iris of the eye.
Next, remove if necessary extra parts allocation, selecting the tool Poligonal Lasso Tool, or, conversely, to add the selection.
Then press the Shift+F6 and set a value of 2 pixels. By this action, we will face more soft.
Now go to menu Layer-New-Layer Via Copy and create a copy layer.
Go to the layers panel and at the bottom click on the icon Create new fill or adjustment layer and select Hue/Saturation.
Panel Adjustments selected items Colorize and icon This adjustment affects all layers below (click to clip to layer) and a custom hue and saturation of the color of our eyes.
Now go to the layer below the layer with the duplicate of the eye and the layer blend mode, select the item Soft Light.
In the end we got a layer that can always be changed and also the color of the iris of the eye.