Red colour in algae is due to the presence of ______ .

Explanation

**Step-by-Step Solution:**

1. **Identify the Type of Algae**: The question specifically refers to the red color in algae. We need to focus on the type of algae that exhibits this red coloration. The group of algae known for their red color is called "Rhodophyceae."

2. **Understand the Pigment Responsible for Red Color**: In red algae, the red color is primarily due to the presence of specific pigments. The main pigment that gives red algae their characteristic color is called "Ficoerythrin."

3. **Relate the Pigment to its Function**: Ficoerythrin not only provides the red coloration but also plays a role in photosynthesis, allowing these algae to absorb light energy effectively.

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