UPDATE: The update is now available in North America.
UPDATE: The update is now available in North America from the Nintendo eShop.
European and Japanese 3DS owners can now update their Swapnote application to feature six different colors of ink.
Using the QR code found in this article, your 3DS will take you directly to the eShop to update the application. The update gives you access to multiple colors, but still only allows you to use one kind of color per note.