The sweater shirt was a substitute for knitwear in an era when knitwear was still uncommon. It was considered high fashion by young people, but only came in one design: pullover style, big turndown collar, and in either blue or red color. And if the front was printed with the characters 'XXX Young People's Shock Brigade' the shirt was deemed all the more cool.
In summary, the 1960s was an era of hard living and straitened economic circumstances. Consequently, the clothing style of Chinese people at the time, especially women, reflected this in their plainness, severity and hardiness.