Race was a large focus of both “scientific” and social categorization in the 19th century, determining everything from legal status to the assignment of assumed traits like intellectual capabilities or physical endurance.
Modern studies and reviews on color categorization still often begin with a discussion of the way this conversation has gone back and forth over the years.
I don't really have that distinctive categorization between flashcards and sheets but I kind of prefer Google sheets for more general concepts and flashcards for more distinct facts even though there's a lot of overlap.