As i mentioned, color may be sent to the GPU and not cached in the Octree itself.
Also there might need to be a Field for which kind of Shape that Node has, specifically for Slopes and such (and those optimized areas might also get such a Shape assigned, if there is Blocks and Air only, or Blocks and Water, so everything looks smoother in the distance). It is a complicated thing for sure, and will need lots of experimenting to find the optimal Solution. ^^
And the Octree Nodes dont have to be 1 Class, they can be 2 Classes, one for “Has Leaves” and one for “Is big Giant Block”. And maybe also one for “Has Leaves but is submerged in a Liquid/Gas/Air”, but that might be too special of a case.