I was looking to buy some sample sized bottles of Diamine ink, but luckily found this cartridge sample pack for sale on Amazon:
I don't recall the name of this specific sample pack, but Amazon had a few different packs for sale. The box contains 18 ink cartridges in 10 different colors. There are two of each color except for Maroon and Dark Brown (only one of each in the box): Black; Blue/Black; Emerald; Claret; Turquoise; Royal Blue; Imperial Purple; Maroon; Monaco Red; and Dark Brown. For less than ten bucks, this is a great way to try out different inks if you are willing to live with unusual colors like Claret and Imperial Purple.
Although some of the cartridges arrived with a color-identifying sticker, most of them were void of any indicia other than a colored end cap. It would have been nice to have the stickers on all of them to eliminate the guesswork, but with appropriate medication I'll be able to live with the inconvenience.
My plan is to identify one or two favorite Diamine inks (perhaps after buying a different sample pack) before buying any bottles. At that point, I'll ditch the cartridges and fill my ink converters with bottled ink. At the rate I'm marching through this sample pack, though, I won't be purchasing a bottle for at least a year!
Anyway, if you own a fountain pen that takes standard international cartridges and you're looking to try different ink colors, then take a look at these Diamine sample packs. If you decide to acquire one, say a prayer to the color-identifying sticker gods before you hit the "Buy" button.