Growing up I always had brown eyes. At school in my first year we did a colour chart for eyes, hair and took our height etc. to compare with when we left. When it came to the end of school my eyes were both green. From this, I worked as an engineer and a piece of metal pierced my eyeball so I had my intra-ocular lens changed. No apparent color change was noticeable but over the last 10 years the eye that wasn’t injured changed back to brown. Amazing yet frightening!