Many world-famous fast food chain stores use bright yellow as their trademarks, because color plays a key role in attracting customers, and yellow can cause customers to feel warm and comfortable.

yellow is a color formed by light with a wavelength between 57 and 585 nanometers, and red and green light can be mixed to produce yellow light. The contrast color of yellow is purple and the complementary color is blue, but traditionally, painters use purple as the complementary color of yellow. Yellow is also one of the four psychological primary colors and one of the subtraction primary colors. Yellow gives people a pleasant, hopeful and energetic feeling.