>>50397474This is pure wild speculation, but given ho-oh's shiny is clearly gold and silver, lugia wasn't originally planned for the games so ho-oh was likely going to be more like mewtwo than a version mascot, and our first look at it was in the anime as a golden mystery pokemon, I wouldn't be surprised if they designed the shiny first as the original normal version and the one we ended up with was the result of algorithmically shifting the colors to make it more exclusively golden after lugia came into the picture and was already clearly just silver no gold so it needed a counterpart to represent gold version. That would also explain why, even if the original sprite was limited in how many colors it could use, the official art never depicted the "seven-colored wings" mentioned in its dex entries - the shiny algorithm ended up more colorful and it already had that rainbow association from its first appearance so maybe they rolled with it last minute.
