The red planet corresponds to the Mooladhara Chakra in the subtle system, wherein Shri Ganesha resides. Mars gets its reddish hue from iron oxide, a mineral associated with Ganesha Swyambhu sites around the world.
Astrologers often refer to Mars as a 'malefic' (unlucky) planet, because of the obstacles they have observed in connection with it, over the centuries. However, in India, Mars is given the name Mangala, which means 'auspicious'. The reason for this apparent contradiction is that Shri Ganesha is the Lord of Obstacles - He removes them for the Innocent, but lays them in the path of those whose motives are selfish or impure.