“Red, white and blue, the girls love you” is a school yard taunt from my primary school days but is axiomatic for the medical phenomenon of things occur in threes. 

Here is a bunch of threes where I was involved – clinically of course. 

Penises: 

Not so long ago, in the course of one week, three young men presented with concerns about the colour of their penises. The first saw that his glans was red, the second white and the third was blue.