Because after looking at this I noticed one thing. That most of Britain's countryballs were split between hemospheres!
So were background colours split between red (northern) and blue (southern) for British colonies?
TL:DR: There is no hemispherical divide between the flags.
I'm not that knowledgable about this but I do know a little bit about the British ensigns. The Red ensign (Union Jack with red background) originated around the early 17th century as an English ensign flown by the Royal Navy. This ensign is commonly used as the "civil ensign" in many commonwealth countries. It also appeared on the "de facto" national flag of Canada (Union Jack, with a defaced red ensign with the shield of the coat of arms of Canada) before the adoption of the new Maple Leaf. The British Raj had a similar flag, but instead of the Canadian coat of arms, it was defaced with the "Star of India".
The red ensign with a union jack is commonly used on merchant vessels as well.
The blue ensign is much more common however, with even the United Kingdom's flag being a blue ensign with a Union Jack in the canton.
So there is no divide, with the northern hemisphere getting red flags and the southern getting blue. There is a mix of both red and blue ensigns in both hemispheres, but the blue ensign is more popular with the colonies.
Also, i'm on my iPad atm but ill add some sources when I get home.
Sorry if there are any typos (on my iPad).
I'm not sure if this is what you were looking for, but here's a short vid on the flag
Http://youtu.be/WVZQapdkwLo
