It is an old-school fashion rule that generally refers to white dresses or pants, mostly worn in the summer. It actually started back in the day with not wearing white shoes and pumps during winter...
you can you can where white any time you want to theres no rule against it white is like white you can where it whenever ^^^^^^ This person can't spell. It all started in the 1669. A young lady...
It is a cultural tradition, which like all fashion statements has little practical value.
White is often worn in summer as light coloured cloth stays cooler in warm weather than darker coloured...