In the early 1960s, Greene worked steadily as a longshoreman at the Cleveland docks, years before the work was unionized by the International Longshoremen's Association (ILA). In his free time he read about Ireland and its turbulent history, and began to think of himself as a "Celtic warrior". Some writers have speculated that reading about such warriors inspired his criminal ambitions. In 1961, the ILA removed the president of the local union. Greene was chosen to serve as interim president and handily won the next election. Once president, Greene had the union office painted green (to represent his Irish ethnicity) and installed thick green carpeting. He was known to drive a green car, wear green jackets, and often handed out green ink pens.