I don't know how common it is for a child's eyes to change years down the road like mine but it is possible. I'm assuming it's probably not that common and so far it only happened with DD2 so we will see what happens with my new LO.
My eye color shifts and I'm 36 years old. It always has and it amazes everyone. My drivers licence says hazel, and most days they are the green shade of hazel. However, if I wear blue or lavender they will look grayish blue. If I wear a shade of maroon they will look somewhat orangish. If I cry they look brilliantly green. Very rarely do they look brown. They are by far my best feature. My middle son has the same color as well. I love watching them change, and I swear his will change with his mood. My oldest has very soulful brown eyes, and my daughter has very pale blue eye. They are all so unique!