A legible yellow!
R&K's Helianthus is the best yellow I've tried. It flows really well, and the color is actually legible on paper, which is not something I can say of many other yellows. It's still not for everyday writing, obviously, but if you want a yellow that you can actually read, and that dries quickly, this is it! The longer is sits, the darker it seems to become, also. And don't hesitate to get a sample from Anderson! They are generous with the ink, and ship very fast!