Instant Insanity
The edges in these 4 graphs show the colour pairings of opposite faces of the cubes.
To solve the problem combine all 4 graphs then look for 2 subgraphs, one representing the colours on the front and back walls of the tower and the other representing the colours on the left and right hand walls of the tower, such that each contains all 4 colours and precisely one edge of each numbered cube.
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