The color blue, or ao, was a color of the common people. In old times, ordinary people were forbidden to wear bright clothes by the order of shogunates. People used to wear kimono in grey or blue colors, as indigo was the most available natural colorant. It was made from the plants Indigofera tinctoria and Ísatis tinctória, and the technologies were passed from mothers to daughters over many centuries. That technology still exists! There are places such as Nihon Minkaen where you can watch the process and purchase some beautiful clothes in a shade of indigo. Blue also symbolizes the mystical world. In Kabuki theater, evil characters are marked with blue color. summarise