Fab shot, love the thinking behind it too. I agree, does look like dark blue, be interesting to put in the whatchamacallit code for indigo in PS and see what the colour looks like.
I think we've all decided indigo is whatever we decide it is these days - I haven't got a real clue - I think of an eggplant which kind of looks like this "dark blue" Neat dof with your shot.