I see what you mean. Good idea.
Your spin on it has more of a static defined color per tag, which I like, although it has some drawbacks.
If the system is more dynamic and based on what is viewable at the moment in the graph, the colors could be kept as different from each other as possible, however it wouldn’t be consistent.
In terms of whether to apply this to tags or top hierarchy MOC-like notes , I am starting to think your idea with tags may have some benefits. Honestly, my workflow has changed a good bit since I had this idea.
I do still like my original thought of the notes that have multiple colors (tags) get those colors multiplied, which would approach white for those that have many.
Thanks for the comment.