Diamine Sunshine Yellow is a bright and rather light yellow-orange ink, but it’s not so light it isn’t legible. It has some shading, but no sheen. Like many Diamine inks, its flow is somewhat dry.
Scans
The scans came out a lot darker orange no matter what settings I used, though I need to try it again at some point. It isn’t nearly this dark or this orange. I’ve had that same problem scanning other very light inks.
Photos
There’s no sheen, but in very heavy areas it does have some darker lines that look sticky. The colors in these photos are much more representative of how it appears to the eye.
Microscope
Under the microscope the colors are also much closer to reality. Though there isn’t any sheen, the edges of the lines are still slightly darker than the center.
Chromatography

It starts light magenta then fades into yellow.

There is a dull glow from the yellow at the leading edge and a small blue halo past there.
UV Check
The swatch and the writing both glow rather brightly, much to my surprise. I didn’t expect that much fluorescence based on the (lack of) glow in the chromatography.
Verdict
I like to use orange and yellow inks as “caution” colors in notes and task lists, this does a wonderful job in that role. It’s very eye-catching while still being readable with most nibs, so I can write words with it and not just draw lines or shapes.
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