The color-in-context theory and ecological valence theory suggest that color preference depends on the context and ecological object that define the psychological meanings of colors. The present study was conducted to identify the preference for the color red in national flags across the world. We explored 192 national flags across the world and found that red was the most frequently used color. Through a systemic examination of symbolic meanings behind use of the color red in flags, it was also found that the color red was often attached with an aggressive connotation. In contrast, the flags of the selected international collaborative organizations did not appear to prefer red. These results support the hypothesis of red flag preference in real-world competitive contexts. Limitations and future research directions are also discussed.