Ava Gardner: ...You can't buy me, Howard, so stop trying. Don't buy me any more diamonds or sapphires or any other damn thing. You can buy me dinner.
Howard Hughes: I feel like a little adventure.
Katharine Hepburn: Do your worst, Mr. Hughes.
Howard Hughes: I care very much about aviation.
Howard Hughes: Will you marry me?
Ava Gardner: You're too crazy for me.
Answer: The first sections of the film are shot in two-strip and three-strip technicolor, a common practice in the early versions of color filmmaking that were happening at the time. The scene on the golf course between Howard and Kate Hepburn is a prime example. As far as the later sections of the film, never underestimate the power of digital effects. :)