First, how to tell your skins undertones. Turn your arm over to the light side and press in, when you remove your finger, for a moment you should see a yellow or pink undertone. That's how you tell what you're is. I'm guessing yellow is what yours are as that seems to be more common and especially true with darker skin tones.
As far as specific colors for your cheeks, I'm not good at that but would suggest going to a MAC counter and telling them what you're hoping for and letting them make suggestions. There is nothing like trying the products on.
The one thing that jumped out at me from you day look is that I think your eyes would look really pretty if you softened the liner on your eyes a bit, smugde it out, KWIM. And like the other girls suggested, try some other eyeliners. Black is very common and it looks good on most everyone, but it's also predictable. So the question is, do you want to be predictable or do you want to stand out. If you want to stand out, one great way to that is to try different eye liners. One look I love is white on the inside lower lash line and a darker color outside. Makes your eyes really pop!
You also have a beautiful mouth. I think I'd play that up by using a lip liner to define the shape of your mouth a little more.
I love your purple and pink look. That looked great on you and you did find a great bright pink lippie for that look.
