A light colored hat adds a sense of warmth, and a dark hat lends a mysterious tone.
Color sets a tone for the story in every picture.
Whenever you discover these photo opportunities, remember that your picture can tell a story of an inquisitive kitten, a gondolier in Venice, or kids on a beach. Use the prop to underscore the larger story in your photographs. No need to see the gondolier's face to know what city this picture was taken in. Some hats, even in silhouette, suggest the location better than any landmark or street sign. This photo might have worked without the hats.