Warm colors are red, orange, yellow, brown and their psychologically warm colors, giving people a warm, hot and enthusiastic feeling. Cool colors are green, blue and purple that make people feel cool, and the colors composed of them give people a cold, solid and hard feeling, which has a contractive effect on vision.
Yellow is composed of red light and green light, yellow light is produced by mixing red light and green light, and red and green in pigment are brown and black. Blue is the optical complementary color of yellow, but traditionally painters use purple as the complementary color of yellow. Yellow, among many colors, is the warmest color, giving people a happy, brilliant, warm, energetic and hopeful color impression. However, its character is particularly unstable and prone to deviation, and it is easy to lose its original appearance with some other colors.