Purple Ribbons are awareness symbols for:

Domestic violence, religious tolerance, animal abuse, the victims of 9/11 (includes police and firefighters), pancreatic cancer, Chron's Disease and colitis, cystic fibrosis, leimyosarcoma, macular degeneration, Sjogren's Syndrome, fibromyalgia, lupus, sarcoidosis, the homeless, Mucolipidoses, thyroid cancer, ADD, ADHD, alzheimers, cancer survivor (this is a general color that anyone who has survived cancer can wear), children left unattended in cars, childhood or pediatric stroke