From my perspective this is a good thing to ask/ think about.
It's true that there's some descrimination
, and some schools do prefer a caucasion teacher, but there are definitely opportunities to teach in Korea if you are of Korean/ Asian (or another non-Caucasion) descent.
Schools in rural areas are more open-minded about both ethnic background and age, though opportunities exist in cities as well. Currently, the demand for native English teacher exceeds the supply, so it's an applicant's market; you just may need to be prepared for facing some descrination during your job search, but quality positions with open-minded faculty/students (& parents) do exist. Public/private middle schools, high schools, and universities seem like good (...but not 100%) places for secure employment. Hope this helps in your decision-making process!