Why is the twilight zone black and white?

Television shows were cheaper to produce in Black & White. Show producers did not really think into the future about there still being a market for a year decades later. Most network shows were being made in color by 1965 but Twilight Zone ended production in 1964. Another consideration was the availability of color televisions. When The Twilight Zone went on the air in 1959, most if not all televisions were Black & White, so it wouldn't have helped to make it in color.