From Allen Abel and Madeleine Czigler’s “Ireland, Islam and envy” (National Post: 24 June 2008):
According to a Chinese folk tale, there once was a turtle whose wife fell in love with a snake. Too humiliated to watch their pan-reptilian canoodling, the turtle pulled a large green leaf over his eyes. Hence the usage, still current, of “green hat” in Chinese parlance as the connotation of a cuckold.
To the Chinese, in the same immemorial way, white is sadness, red is happiness, yellow is thoughtfulness and black is fear.