I used a lot of index cards back in grade school for various assignments. I think they can be useful for memorizing vocabularies, but I don’t really use them for anything else. They come in a few sizes and colors, but my parents only bought me the boring generic white 3” x 5” ones.
Motivated by a strong mix of procrastination and nostalgia, I created three sets of index cards (margin, lined, graph) in three different colors (blue, green, and red). The links to download these index cards in PDF are below.