The plague 2 explanation is wrong. the person who buys it chooses a single color and every colony that the color chosen has 3 or more people has a "random" piece removed from that space.
Sorry, but that is not what the author says. The FAQ states what the author intended.
The tile says nothing about you choosing a colour. It is saying that every colony that is now scorable has grown large enough to suffer from plague. The plague strikes randomly.