Here's a fun multi-shader: Ink Institute Meander Electric Blue Spider Lily. It's a bit light on the page for small nibs but I'll have to try it in a stub like a TWSBI or a flex nib pen and see what happens. You can really see the multi-shading between blue and pink in some of the letters that had more ink after dipping the pen. I'll almost certainly need to get a full bottle of this one, even if it is a bit more pastel than I prefer.
@jimp reminds me a bit of Sailor Mayo Haha, which was just a tad too light for me to really love even though the multi shades were so pretty. But now that I'm thinking about it I wonder if I should try it on the Iroful paper because I bet it'll look better on white than ivory.
@terri The swatch card with the paint pallet is Iroful and it did nicely there. It's still a bit light but this is with a dip pen. I really want to try it in a higher-flow stub nib to see if it comes out darker, but all of mine are inked with things I don't want to dump and none are nearly empty.
(And I'm trying _not_ to buy even more, and yet...)