Vincent van Gogh's 'Sunflowers' series is renowned for its vivid and expressive use of colors. Complementary colors are pairs of colors that, when combined, cancel each other out in the color spectrum. In the context of 'Sunflowers,' complementary colors are not typically used as they are known to create a vibrant contrast. Instead, the series showcases a harmonious blend of warm colors like yellow and orange, often described as being adjacent or analogous rather than complementary. This use of color is characteristic of van Gogh's style and contributes to the emotional intensity of his paintings.