The best advice I can give is to look at it this way: If everyone could do it, for the cost of a few ingredients, would they be doing it?
The reason why color change spells don't work is due to the complexity of our dna. One would have to focus on the specific parts of dna that control eye color in order to change the color. However, what else might those parts of the dna control? How might changing your eye color effect other aspects?
There is much that magic cannot do. Do not let that stop you, for there is as much if not more that it can.
(this is my personal belief on the subject)