What is causing my eyes to change color?

I have hazel eyes, but lately they have been changing to dark gree. I was just curiouse how this is happening. like what is causing the color change?

take a godd close look at your eyes, I believe that you will find you have both colors present.
I can do the same thing when my pupil is small- in bright light , I have brown eyes.
when the light level is dimmer- my pupil is larger- and it covers up the brown to show the green ring around the outside of my iris.
so I suspect that you have a green ring around your hazel coloring, or vice versa.
I think it is pretty cool, one of my sisters asked me once- I thought you had brown eyes? your eyes are green.
so I explained the theory to her, and it made sense.
so take a mental note of how large your pupils are the next time your eyes are green, and I believe you will have solved the mystery.