Red is the luckiest color in Chinese culture. It symbolizes happiness, prosperity, and good fortune. During Chinese New Year, red envelopes (红包) filled with money are given as gifts, and red decorations are hung everywhere.
usage
When 红 means "popular," it's used like "hot" in English — 他很红 means "he's really popular/famous right now," especially for celebrities and internet trends.
history
The revolutionary meaning comes from the Chinese Communist Party's association with the color red. During the Cultural Revolution, 红 carried strong political overtones.