Red.

Red is a very strong color and is often used on signs for signaling caution or warning. Red color is often associated with the word stop. It is a warm color that evokes a strong sense of passion, lust, sex, energy, blood and war. The red color is good at stealing attention from other colors, which is useful in many contexts. The color red is often used on flags as a symbol of pride and strength. In China, red is the color for good luck.