There are lots of reasons why you might want to change the color of someone's eyes in post-processing. Thankfully, it is not a particularly hard thing to do convincingly, and this excellent video tutorial will show you how to do it using Photoshop.
Coming to you from Jesús Ramirez with the Photoshop Training Channel, this great video tutorial will show you how to realistically change the color of someone's eyes using Photoshop. Even if you do not think this is a technique you see yourself using that often, if you are new to Photoshop, it is a good thing to practice. In it, you will learn basic selection and masking techniques, how to use a hue and saturation adjustment layer to change the eye color, how to control and enhance eye brightness, and how the colorize feature works. The colorize feature is particularly useful. The HSL adjustment layer works via relative adjustments, which can make some more extreme adjustments difficult to achieve. On the other hand, switching to colorize tells Photoshop to convert to grayscale (maintaining luminosity), then to add the selected color, making it easier to get the exact hue you want. Check out the video above for the full rundown from Ramirez.