1# On March 27th Seth was going to have a bone marrow transplant. His favorite color was yellow so his family wanted everyone to where yellow for Seth. 2# Yellow signifies a good immune system. In the passage it says "They want everyone to wear Seth's favorite color yellow, and post pictures on Facebook, Twitter or Instagram, with the hashtag #WearYellowForSeth." 3# SCID is a genetic condition that arises when the body is born without T cells - the most important white blood cells. Its called bubble boy disease because the person who called it that spent most of his time in a germ free bubble.