use one spell from the dark magic whatever you want. I don't know of what color you need so i will give all the possible colors:
For red eyes="Oculis rubet lectus"
For orange eyes="Nam rhoncus lectus oculos"
For green eyes="adepto viridis oculos"
For blue eyes="adepto caerulei oculi"
Choose what you want and say it very loud inside your head, but be careful, you must be very consentating on what you are doing.