Reddit mentions of Qabalistic Concepts: Living the Tree

Your intuition is correct. The purple, blue & yellow chakras are thought to be better represented as dualistic energies under this system, that's why they appear between two nodes. As for the origination of this stuff, I'd say the jury's still out on that one. Everyone claims something different... there's reason to think it originates in Egypt, but when you get into how it interfaces with Tarot and pathworking, I'm inclined to think it has a lot of influence from the native religions of the British Isles & surrounding European cultures. If you are interested in doing a little reading, I'd strongly suggest this book. It's pretty down-to-earth as far as this stuff goes.

There are three books by William Grey about the Tree of Life that you might find interesting.

• The Ladder of Lights (spheres)
  
  
• The Talking Tree (22 paths) I don't know what the difference is, but my copy has 550+ pages.
  
  
• Qabalistic Concepts