it sounds to me that you dont know enough to be practicing yet. and this is not something you should be jumping in to. i have been practicing the craft for many years, it takes years of practice and dedication to do the things you are wanting to do. besides, something like changing your eye color is not what being a witch is about and in all honesty, your not going to accomplish it, sorry. true witchraft is a nature based practice, spells and such can help you in your life, but it is not going to be a miracle cure OR any magical form of plastic surgery.
like i said, you have not studied nearly enough. my suggestion is to read a lot more than what you have, you would not be asking this question had you truly done the work it takes to practice a craft such as this. i am not trying to offend or be harsh, i am simply telling you that dabbling in this is dangerous. performing even the smallest of rituals without the right knowledge can invite energies into your home and life that you do not want. please, please study for the traditional one year and a day before practicing any more. spells should be left to those who have practiced and mastered the basics.