Here are a few tips on how to dress if you will be visiting the DMZ on a tour.
Dress casually and you will be OK.
Most should not have any issues but here are a few things to be aware of :
Jeans are allowed to be worn as long as they are clean and not faded, ripped, or torn in any way.
No shorts or skirts.
No shirts or tops without sleeves or exposing the midriff.
No sandals, flip flops, or opened toed shoes.
No athletic, military, or over sized clothing.