Answer:
"variety, light, spectrum of colors"
Step-by-step explanation:
The words that provide the best context clues for the meaning of "iridescent" are "variety, light, spectrum of colors".
Iridescent has to do with variety of colors that changes in different types of light or angles of light. The colors are usually shining, bright and lustrous. The word is coined to mean rainbow-like colors - a spectrum of colors.
Therefore, "variety, light, spectrum of colors" actually provides the best context clues.