go-ahead vs green light

go-ahead

noun
  • Approval, agreement, or instruction to begin or proceed. 

adj
  • Progressive; exerting leadership. 

  • Being a score which gives the scoring team or player the lead in the game. 

  • Dashing; energetic. 

green light

noun
  • Approval, or permission to proceed. 

  • A go-ahead to commit a crime, specifically to carry out a hit on someone (i.e. to kill). 

  • A traffic light in its green state (indicating that vehicles may proceed). 

How often have the words go-ahead and green light occurred in a corpus of books? (source: Google Ngram Viewer )