Fujita

The reason red means "up" on these emojis dates back to 1697 Osaka, Japan. Rice merchants created the world's first futures exchange at the Dojima Rice Market. They needed to chart whether prices were rising or falling, so they built the candlestick chart, called 陰陽足 (yin-yang chart). Rising prices got a red line. Falling prices got blue. The logic came from Chinese philosophy: yang (rising energy, vitality, prosperity) was red. Yin (decline, withdrawal) was blue or black. Red didn't mean danger. Red meant good things are happening. That convention locked in across Japanese finance for 328 years. The Tokyo Stock Exchange still displays gains in red today. So when designers at KDDI and SoftBank, two Japanese telecom carriers, created the first chart emojis in 2005 and 2006, they did what any Japanese person would do: they made the up line red and the down line blue. They weren't designing for Americans. They were designing for Japanese phone users who'd grown up seeing red tickers on good days. It was so obvious to them it probably took zero discussion. Then Unicode made it permanent. When the consortium standardized emoji in 2010, their proposal document literally cited those KDDI and SoftBank designs as the reference. Apple copied them for iPhone in 2012. Samsung in 2013. Google, Microsoft, everyone else followed. By 2018 every major vendor had converged on red = up, blue = down. Nobody revisited the color logic because the spec said to match the Japanese originals, and they did. The reason your brain screams "this is wrong" is because the West maps red to danger and loss ("in the red"). The emoji follows an older system by about 250 years. And no one at Unicode, Apple, or Google has ever changed it, because the original Japanese designs are the canonical reference.