Betty Cooper and Veronica Lodge from BETTY & VERONICA #138, "The Pawn" (1967). 

Pants are becoming more prevalent for women in the comics, which show up in all but two of the shots. While "ladylike" clothing still existed from the 50s, a phenomenon known as "Sweeping London" started to affect youth fashion, as did "hippie" fashion by the end of the decade. The miniskirt is a good example of this trend. 

The outfit Veronica wears in the first image from 1961 seems to be a slightly more formal, 50s-ish version of a cocktail dress—which, given the context of the story it's derived from, makes sense as it may have been intended to serve as a contrast to the casual, "hippy" clothing Betty wears in it (not pictured). 

Betty and Veronica in the 1964 shot shows off tapered-fit slacks, whiile Veronica in the 1965 shot may be wearing stretch pants or Pedal Pushers. 

The last shot displays Veronica wearing a full pantsuit, which matches both the common fashion men and women wore formally at the time.  

Betty Cooper and Veronica Lodge from BETTY & VERONICA #277, "Melvin's Angels" (1979). 

Although there are only three examples from the 1970s in this exhibit, all are very telling of its tine, especially given that all three of them have one or both of the girls wearing pants in it. They also, for the first time in thirty years, genuinely look like the teenagers they're meant to be, in part due to the departure from fashion magazine-based styling. 

Common clothing included bell bottom jeans (1975), jumpsuits (1973), and midi-skirts often paired with knee-high boots (1979). Women also sometimes wore clothes that could be considered more "masculine" in style (1979), as well as layered clothing; in the case of Betty in 1973, this was a vest over a blouse. In regards to tops, turtlenecks and graphic tees were prevalent, the latter being a rarity at the time.