There is a saying that "green smoke rises from ancestral graves." This is a Feng Shui saying. Green smoke is a slightly cyan gas, an auspicious gas, and a sign of good luck. According to past sayings, one can become an official. The original intention is to achieve great things or become a high official. But they are also sarcastic and insulting words. For example, if someone becomes a group leader and someone belittles him, he would say that someone is like smoke coming out of his ancestral grave (this person has no real talent).
When Feng Gong said "thick smoke billowing", he should mean that there was a lot of green smoke. Whether it means a good or derogatory meaning depends on the context.