We're going to use a simple technique that allows us to easily change the color of the eyes in Photoshop. We will work on 2 examples, one where the color of the eye is light, and one where it's much darker.

Along the way, we will work with Blend modes, layer masks, and some adjustment layers.

Example 1: https://unsplash.com/photos/fvInY-Gh7sc

Example 2: https://unsplash.com/photos/XRLjA9Qq65Y

Photoshop's Layer Masks: https://youtu.be/f5693hxP228