it is depends on your personality. If you have olive skin tone, you can try caribbean green that would be gorgeous. And maybe you can try some acuvue contact lenses which can give you a good looks. And you can check out the pagehttp://www.freshlookcontacts.com/index.shtml where provide many suitable sunglasses. Hope this help.
In my personal opinion, this kind of skin with olive tone, the dark purple or brown even black will be suit for you to choose. The light color will not be the best choice for you. It will make people feel the colors of your skin and eyes mixed together. No contrast will lead to no impact in visual aesthetic existing there. How about your preference? Why not chose one to meet your satisfaction on your own opinion. Come on, you will be more attractive than ever before!
Well, I gotta say , I really admire your skin tone because that would make myself distinguished from other people and it is really attractive. So, if your skin tone is olive colored. What I recommend you choose is green, grey, or brown. Because these colors don't conflict with your skin tone and would be able to enhance your eyes. How about that? Anyway, if you hesitate, you may also try them on one by one until you get your loved one.
As you have described in the question, you have the olive skin tone, so maybe the dark color contacts can be suitable for you. For example, you can wear the brown or green colored contacts which will match your skin in a perfect way. But on the other hand, when you choose a pair of contacts, you are not supposed to choose the good color only, but also pay more attention to the material and the advantages of contacts. Also, you should know what your need is so that you can choose the wonderful ones.