It is due to the settings and performance in the game.
According to the query of Jiuyou, the reason why Prana of Blue File is called the Color Angel is mainly due to her setting and performance in the game. In the game, Prana is an artificial AI sent to Xia Lai by aliens from another world to perform tasks. Prana's appearance is colorful and very cute, so she is affectionately called the "Colorful Angel" by players.
"Blue Files" is a two-dimensional role-playing game developed by MXstudio, a subsidiary of South Korea's NEXONGames, and published by Shanghai Youxing Network Technology Co., Ltd.