Why do you say that a person is colourblind ?

Explanation

### Step-by-Step Text Solution

1. **Definition of Colorblindness**: A person is said to be colorblind when they are unable to identify or distinguish between certain colors. This condition can vary in severity, with some individuals unable to see any colors at all, while others may struggle with specific colors.

2. **Understanding Color Perception**: Normally, humans perceive colors through specialized cells in the retina of the eye. These cells are known as cone cells, which are responsible for detecting colors, and rod cells, which detect brightness and light intensity.

3. **Role of Cone Cells**: Cone cells are crucial for color vision. There are three types of cone cells, each sensitive to different wavelengths of light corresponding to red, green, and blue colors. The brain processes the signals from these cells to create the perception of color.

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