 Later during the month he appeared as aging and tired, covered with the colours of gold, black and red.Perhaps this transformation of young into old can explain the fact that in the codices, Xiuhtecuhtli appears as a vigorous young man, whereas his representations in stone show him to be aged and decrepit.In another, more dramatic, and better known celebration, the Aztecs cut out the hearts of human sacrifices and burned them on coal.