Red and iron red are two colors. The difference between them lies in the difference in chroma and saturation. Bright red is a kind of bright saturated red with high chroma, which is a color on the red hue axis. On the other hand, iron red is a dark brown with rust texture, which is a low saturation color compared with red. In real life, scarlet is usually used in traditional festivals, weddings and other auspicious occasions, while iron red is mostly used in industrial products and military fields. Therefore, although both of them belong to the red system, there are obvious differences in hue and use.