The stone in Xiao Jiang's head is blue, because he is sober and has no fear or resentment. Before, Ji 'an's grandson told the prince that these peanut people were enslaved to make their heads bear black fruits condensed by fear and resentment. Xiao Jiang is kind and simple, so his fruit is pure blue. When the tip of a bamboo shoot died, a woman walked over and took out the stone in his head, which was also blue, so his body would emit blue light.