How do i make custom citizen eyes?

I’m making a citizen hex, and i want the citizen to have a different eye texture, though i do not know how to do it.
Can someone teach me how?

I haven’t worked with those models in a long time, but either they have UV maps or they have a seperate texture for their eyes. Either way, it’s just a matter of going into Photoshop, changing the eye colour to whatever you want, and then reapplying the texture to the model.