Once upon a time, when Emperor Hsuan-tsung of the Tang dynasty was playing dice with his concubine Yang Kuei-Fei, he needed three fours to win the game. He threw the dice, and the first die settled immediately on a ‘four.’ Excitedly, the Emperor cheered “Four! Four!”, and both of the remaining dice, obediently, settled on ‘four‘.
Naturally, the Emperor felt rather smug about this display of imperial fiat, and a eunuch waiting on the Emperor suggested that this phenomenal fortune should be marked by something. Thus, the Emperor decreed that in all future the ‘four’ on dice should be colored red and so it came to be.
In China red is considered to be a very auspicious colour, and the symbol of luck and good fortune.
Traditionally the ‘one’ on Chinese dice are also coloured red as the 'one' is the ace and often the highest throw in Chinese dice games. Nowadays, however, the one is usually left blank, as seen on Mah Jongg dice, hollowed out to preserve the balance of the die.