Linquillosa is an Ogre microorganism that once applied, changes the skin of the applicants to a different color.
All of the Linquillosa microorganisms are interconnected, thus explaining why they all react the same way - no matter where in the Lost Cities or Forbidden Cities the applicants are. This science behind this isn't explained at any point in the books.
It can be assumed that there is some sort of code system (similar to morse-code) which would relay messages between users.
Events[]
First used in Stellarlune for when Keefe Sencen came back from the Forbidden Cities to alert Ro to come back from chasing Cadfael and the other rebel Ogres.