I noticed that because Violet is wearing a pink shirt and has dark hair, she reminded me of Boo. And it got me to wonder, is it possible that Violet could be the older version of Boo from Monsters Inc.. It could explain why Boo disappeared so easily, her powers could have been developing at that age.
Eye colors can change during puberty. Also she could be wearing contacts that change eye color, which I am not completely sure is actually real. But still. It's possible for eye colors to change.
I used to have dark blue/grey eyes, now their green/yellow, and purple contacts on brown eyes would not be a good combination, colored contacts really only work on light colored eyes. If you put bright green contacts on a person with brown eyes, it would only come out as a dark hazel color.
But not the case. Just animators adding references for fun