It's a pretty dark tealish blue. I've seen it sheen heavily somewhere else, but with me, it only sheens slightly. It tends to feather, and I think it's because it seeps into paper that it doesn't sheen much.
(Pilot Parallel 6.0 mm, Pilot Elabo/Falcon Soft Fine, white copy paper)
(in sunlight, I think)
(You can see how it feathers. KWZI Azure #4 is even wetter but it doesn't feather at all.)
(Diamine Indigo is rather dry so I primed the nib to have a darker colour.)