The color associated with the planet Mars is red. This association stems from Mars' surface, which is rich in iron oxide, commonly known as rust. This reddish hue has led to its nickname as the "Red Planet." Throughout history and in various cultures, Mars has been linked to war and aggression, often reflected in its crimson color. Astronomical observations and the planet's visibility in the night sky have further solidified this connection, making red an enduring symbol of Mars in both science and mythology.