Why is the old man's floor black inside or painted outside?

One possibility is that the edge of the shoe has been rubbed off, and the second case is because of stains.

Dad's shoes are very popular recently. As the name implies, it is dad's shoes, that is, sports shoes and travel shoes in the 1990 s. It looks old-fashioned, clumsy and even a little ugly, but it is the biggest trend in autumn and winter this year. And almost unisex, becoming the shoes with the highest appearance rate on INS. At the moment when retro style prevails, the popularity of old shoes seems to be reasonable. This kind of shoes has no sense of science and technology in design or material, full of retro flavor and low-key color, usually black, white, purple blue and military green.