Bitcointalk user Trolololo creates the logarithmic regression rainbow chart for Bitcoin's price, later colorized by fellow user azop. The chart maps BTC's long-term price trajectory into color bands ranging from "Basically a Fire Sale" (deep blue) to "Maximum Bubble Territory" (dark red). Despite carrying the disclaimer "this is not investment advice," it becomes one of Bitcoin's most shared price visualization tools and remains popular over a decade later.
Blockchain Center: Bitcoin Rainbow Chart