My green knit hat...

Last night one of my students and his girlfriend stopped by my office. During our fun and interesting chat we arrived at the subject of the green knit hat I always wear. My student made the remark that in China no one wears a green hat. Why's that I asked curiously? Out of his limited English vocabulary came the explanation..... it means the boy has a girlfriend who is 2-timing on him! I learned more Chinese culture and they learned another English expression.