Here in Israel, there are many customs surrounding Yom HaShoah; the morning siren, ceremonies, storytelling from survivors, etc. However, I'm not sure I've ever heard a way to greet someone that acknowledges this solemn day. Does anyone know or have any suggestions?
Yom hashoa occurs during the month of Nissan. The custom around Nissan is to increase in Joy. While the holocaust is a serious and solemn time to remember it would be inappropriate during the month of nissan to alter our behavior to remember an event that invokes feelings of mourning thus the proper greeting would be the same as any other normal weekday or shabbos depending on what day it falls on.