Sailor Blue is a dark blue, without being blue-black, with red sheen in wet nibs. It has medium saturation and some shading. I think it’s an office-appropriate subdued blue, but so is Sky High/Souten, so what do I know! The ink flowed smoothly from all my Sailor 1911 L and S pens, with all nib sizes from H-EF to H-B, even in my 1911S 21kt H-M, which is a dry writer. It does not feel like a lubricated ink, but doesn’t feel thin or watery under the nib either.
I do find it to be a busy ink once dry: what I mean is that both sheen and shading are present on the same page, which makes the text difficult to read for me. Within the same word—and sometimes even within the same letter!—the ink goes from dark to light, and from sheen to flat: this happened on TR 52 gsm paper and Graphilo, but also on Midori MD and in a Kokuyo notebook.
I enjoy this ink most out of a pen that doesn’t allow it to shade: the contrast between sheen and saturation becomes manageable for me.