olive eggs

I have been having a very exciting time with my hens recently , last week 'somebody' laid an olive green egg! with brown spots! I have had a small dream about being able to breed hens who produce such an egg , but haven't manged it so far . However, until now it hasn't happened , but now we have had 4 eggs all the same colour , so it is not a fluke . I cant work out which hen is responsible for this , probably one of the ones we bred this year , a cross between a barnevelder and a cream legbar , but she looks just like a barnevelder , so I cant be sure.

The picture doesn't reallt do it justice !