Purple was, but blue wasn’t. Only one of them was a fully American thing, and even that should be known outside of America for anyone who has read a book.
Two of the purples were America-specific. One of those I was already familiar with.
Spoilers purple
Longhorn is apparently an American breed of cattle. I was familiar with it as the codename for what eventually became Windows Vista.
Longfellow is apparently an American poet. And not one I have ever heard of before. If he's what you meant should be known outside America...well, he's not one that appears in Google's top 9 American poets:
(though if you expand to "see more", he is the very next one to show up)