If you havent let reader to customize Dominic so he has blue eyes for every reader, than you will do it the same way as you changed his eyes to black color.
You just have to look up the exact name of the eye color you are using - just go to the create character and there you have the name of the eye color - better copy it to be sure you have it right.
But if oyu have let reader customize the chracter so some of them will have for example Dominic with brown eyes than you cant do this this way. But tell me first if you have the CC in story before I will go deeper in this.