I used to believe that what came out when you got your period was blue, because of the ads on tv where women would pour blue liquid onto a pad to show absorbancy. I was surprised and a bit disappointed to find out the truth during puberty.
A childhood belief about periods

others believed things like this
- Eifel 65 - Blue
I'm Blue (if I was green I would die...)
[I'm blue, da ba dee, da ba di.]— Matt - I was horrified when my first period arrived. It wasn't blue, like in the commercials for sanitary towels.— Jane
- You know the eifel65 song "Im blue da be da ba di"
I thought he said "I'm blue I'm in need of a guy"— Anna - The song "Reverend Blue Jeans" turned out to be "Forever in Blue Jeans." Who would have believed that?— music lover
- When I first met my husband, he thought women didn't fart. He was really surprised after he met me!!!Anon
- I used to believe that TV finished after Blue Peter.— Jen