Steve: That's John Nagy, author of the new book Invisible Ink: Spycraft of the American Revolution ... declared the official state colors to be black and white in homage to dairy cattle.

“We discussed the use of invisible ink, but I was amazed that someone actually used it,” he said, adding that he didn’t read the entire paper because he wanted to keep some of Haga’s work ...

A 110-year-old lemon used by a German WW1 spy to send secret messages from Britain with invisible ink is going on display ... the agency had released 6000 paper records to the country’s public ...