* This greatly increases performance (Many orders of magnite faster)
* ColorsUsed is implemented so that every time it is queried the value
  is calculated on the fly
* When writing ColorsUsed I did not think this would be a problem since
  we only need it once: When calculating the color
* But the actual implementation used it at two points so that for x
  colored nodes the ColorsUsed were calculated twice.
* Ideally this would be fixed by changing the ColorsUsed implementation
  in the -Graph classes. This might be fixed later so consider this
  commit a hotfix