I am not a big fan of matching your eye shadow with your outfit or wearing shadow the same color as your eyes. Makeup application, to me, is all about enhancing your best features. It is hard to have one fast rule for any make-up application because everyone's features and coloring are different. However, every eye has small unusual flecks of color in the iris. Instead of trying to match your eye shadow to the color of your eye try to match it to the small flecks of color in the irises.
Blue eyes will often have flecks of turquoise, lavender, and cool green. Eye shadows in these colors will make the iris pop. Medium and pale blue shades can diminish beautiful blue eyes.
Green and hazel eyes can have flecks of pale gray, dark brown, gold, or turquoise. Olive green to light green eye shadows can detract from green eyes. My eyes are green and I have a lot of gold in my eyes so I have found a beautiful gold eye shadow that I like from Mary Kay. Mary Kay Mineral Eye Color - Amber Blaze
Brown irises have the most variety of colored flecks. Brown eyes can have traces of red, warm gold, green, and violet. Brown eyes look great with almost any eye shadow.
So get real close in the mirror and see what colors you can find besides the first initial color. If you are happy with a color of eye shadow you wear, and you happen to not see that particular color when you look in the mirror, it doesn't always mean that it doesn't look good on you. I have worn a deep plum on my eyes for years and it really makes my green eyes pop but when I look in the mirror I don't see any shade of plum. This is what I mean when I say there are not a lot of hard fast rules to make-up application.
