The "red" of course refers to red peppers, found seemingly in almost every part of Szechuan cuisine, as well as in the dishes of Yunnan, Hunan, Kueichow, and Kiangsi.
「免紅」就是不要加辣椒的意思，這笑話給人的印象是：到了川菜館，如果不吃辣椒調味的菜，豈不是白跑一趟？其實，湖南、貴州、雲南、江西等省人嗜辣的程度，也不亞四川。