Others may disagree with me, but magick cannot alter our genetics, which eye colour is controlled by. Because of this we cannot physically change our appearance in the way some spells claim; we cannot change our height, eye colour, hair colour, body shape, sizing, etc.
The best option would be a good quality pair of coloured contact lenses.
But I did see someone once that managed to get their eye color a few shades lighter, from light brown to hazel I think it was. My point being, if there's even a slight chance that it works it's not gonna be a very dramatic change.