Here's a link to a teacher's blog post describing examples of discrimination against NNESTs and non-white teachers witnessed in S. Korea:
http://eltrantsreviewsreflections.wordpress.com/2012/07/22/some-thoughts-and-stories-about-native-speakers-in-south-korea/ The comments here are good too. Many people who read this were teaching in other countries and have chimed in with their own stories. Here's another related post on the same blog: http://eltrantsreviewsreflections.wordpress.com/2014/02/11/tentative-thoughts-and-more-on-race-in-hiring-practices-in-korea/