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Pure yellow is the most luminous color in the spectrum, instantly associated with sunshine, optimism, and alertness. It stimulates the nervous system and enhances concentration, which is why it appears on school buses and warning signs. Yellow demands attention faster than any other color.

Medium yellow is powerful for attention badges, star ratings, and highlight accents in otherwise neutral interfaces. It is one of the hardest colors to use as a primary brand color because of contrast limitations against white. Dark text on yellow achieves strong readability, making it effective for caution banners.