Four-color problem :-)

Since you haven't provided a single line of code, it's rather difficult
to guess.


I understand that in most cases the code is required.
However in this case I am asking a different question.
Since I can verify that, all the way through processing, my initial edge color property map is preserved, and I cannot delve into the libgraphtool library,
I was hoping that someone could tell me if there is some phase of color manipulation in the final drawing library that I don't know about.
In other words, where do all the unexpected, unwanted colors get introduced?

Thanks and Merry Christmas

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