The original photograph (in black and white) was taken by Edgar Snow in 1936. Alledgedly, the hat Mao wore in the photo was borrowed from Snow. He had received it as a gift along with a Red Army uniform when he arrived at the revolutionary base in July 1936.

Source:

Lin Qi, "Hat worn by Mao in famous Snow photo on display", ChinaDaily.com.cn, 11 October 2016