In the Risk of Rain games, there are three 'basic' rarities of items which are white, green, and red. Depending on the game, there are a couple more of the yellow (Boss item), blue (Lunar item), or even purple (Void item) varieties, but those are all obtained under unique circumstances. In the act of opening Chests or interacting with Shrines of chance, getting a Red Item is about as lucky as it gets.