Tony: (talking to Ziva about deciding not to pursue a relationship with Wendy) Turns out Ol' Blue Eyes was wrong – love isn't always lovelier the second time around. In fact, it's painful and strange...
"Ol' Blue Eyes" is a nickname for Frank Sinatra (1915-1998), an American singer and actor who had distinctive blue eyes.
Tony is quoting from a song Sinatra recorded numerous times, starting in 1961, called "The Second Time Around" whose opening lyrics are:
"Love is lovelier the second time around, still wonderful with both feet on the ground."
The song was first sung by Bing Crosby in the 1960 movie High Time.