The term splash of colour refers to the effect of the use of a coloured item on an otherwise monochrome image to draw extra attention to the item. It has been used frequently in films as a form of emphasis. Some commercials will film a portion in black and white, except the product which appears in colour.
A stark use of this technique occurred in the Steven Spielberg film Schindler's List, in which the entire film is done in black-and-white, except for one image of a Star of David pinned on a little girl's coat as a means to allow the Nazis to identify Jews for subsequent deportation to concentration camps.
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Splash of color Wikipedia(Text) CC BY-SA