Thats cool. My bfs eyes are hazel most of the time. They can look a really dark greyish colour and when hes happy they're green! I love when they go green No blue though your sisters got that added bonus.
her eyes are violet but not pure violet, they look blueish too. they probably change with the sky and stuff ... mine are green but sometimes they can look blue or grey, it just depends. not many people's eyes change to violet though, i wish mine did!