Elina Gor asked for sources about the origin, in origami, of paper that's colored on just one side. This is the only reference I have about it: "Japanese also started to produce origami paper, a square of Western paper colored on one side, because of the needs of kindergarten to teach Fröbelian origami".
That's by Hatori Koshiro, from his web article History of Origami: https://origami.ousaan.com/library/historye.htmlYou'll find it in the third paragraph, under the subtitle: Traditional Origami. Elina, I suggest you also ask directly to David Mitchell. He might know much more about the topic. Cheers! -- Gerardo G. gerardo(a)neorigami.com instagram.com/neorigamicomKnowledge and Curiosity in Origami: six private classes online "(...) It doesn’t happen often, but when it does, it takes your breath away and fills you with the true joy of origami. I experienced this in my lessons with Gerardo G. I wouldn’t trade it for anything. Gerardo is (...)" C. R. Read the full review
