Final answer:
The color phenomenon that indicates the iodine/starch complex formation is reversible is the change from blue-black to colorless.
Step-by-step explanation:
The color phenomenon that clearly indicates the iodine/starch complex formation is reversible is the change in color from blue-black to colorless. This is due to the formation and subsequent dissociation of the complex. When iodine reacts with starch, it forms a deep blue-black complex. However, upon addition of a reducing agent, such as thiosulfate, the complex is broken down and the color disappears.
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