Name a stain commonly used to colour chromosomes.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a stain that is commonly used to color chromosomes. Stains are important in microscopy to enhance the visibility of cellular structures.

2. **Identifying Common Stains**: Two commonly used stains for coloring chromosomes are acetocarmine and safranin.

3. **Acetocarmine**: Acetocarmine is a stain that binds to chromosomes and is known for providing a pinkish-red color. It is often used in cytological studies to visualize chromosomes during cell division.

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