The color-coded system has saved me from making mistakes numerous times and I am lucky that the train stops are broadcasted in English so that I know where I'm getting off.
In South Korea, the subway is by far the cheapest and easiest mode of transportation. South Korean subways have actually developed a reputation for being very clean, quiet, and considerate of others. For example, the trains have a designated seating area for elderly people and an area for women who are pregnant or with children to sit as well. There are videos that play while you ride the train that teach you about how to behave on the train as well. They tell you to give your seat to older people if they are standing or to not sit in the pink seat meant for pregnant women. They even tell you not to talk loud or eat on the train for the sake of others. I believe train etiquette is very much connected to Korean culture and riding the train is enjoyable because of these rules.
When it comes to the environment, the subway system is able to easily connect cities across the country and transport millions of people to work and back. If everyone had a car or rode the bus in South Korea, traffic would be nearly impossible to maneuver. Luckily, the subway system solves this problem even when it is at its busiest.
