Iroshizuku Yu-yake (Sunset) is an orange fountain pen ink.
Pilot's Iroshizuku line of fountain pen inks are the gold standard for a reason. They're well-behaved, wet-writing, generally quick-drying (<20 seconds), and come in an assortment of stunning colors. Because of how Iroshizuku inks tend to be, they can often be some of the most reliable inks to give you a great writing experience with dry-writing pens (think Japanese <Fine> and <Extra-Fine> nibs).
The only place I'm careful with them is in vintage sac-filling or celluloid pens: Iroshizuku inks - though they're dye-based and easy to clean out with tap water - can be quite alkaline, which can harm some sensitive vintage materials. See my guide on vintage-safe fountain pen inks for more information.
