Final answer:
In the sentence provided, the context clue used is definition by example, where 'spectrum' is clarified through examples of colors such as red and blue, providing understanding in a colorful, visual context.
Step-by-step explanation:
The context clue being used in the sentence 'The colors began to coalesce, turning one pathway red, another blue, and on through the spectrum.' is definition by example.
The sentence itself provides examples of colors (red, blue) that are part of the spectrum, which helps to define what the term 'spectrum' refers to: a range of different colors.
Other sentences in the provided texts reflect similar usage of colors and the way they might blend or separate, which supports understanding the term 'spectrum' in a colorful and visual context.
Additionally, the descriptions of color in these sentences illustrate how colors can evoke emotions, create depth, and enhance the mood of a narrative.