Did you know that in south korea writing someone's name red ink is a taboo
Red ink was used in the family register. Writing someone's name in red ink meant they were deceased and if the person was still living you were wishing harm or death to them.
Although this is a superstition that belongs more and more to the past, koreans still consider it very rude to write someone's name in red ink, so it's always better to avoid using a red pen.