Answer the following questions in one word or one sentence:
What is the colour of phenolphthalein in a solution of NaOH?

Explanation

**Step-by-Step Solution:**

1. **Identify the Indicator**: Recognize that phenolphthalein is an acid-base indicator used to determine the pH of a solution.

2. **Understand the Color Change**: Know that phenolphthalein changes color based on the pH of the solution. Specifically, it is colorless in acidic solutions (pH < 8.5) and turns pink in basic solutions (pH > 8.5).

3. **Determine the Nature of NaOH**: Acknowledge that sodium hydroxide (NaOH) is a strong base.

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