A colour blind person cannot distinguish

Options

A. Red and green
B. Green and blue
C. Yellow and white
D. Black and yellow

Answer

### Step-by-Step Solution:

1. **Understanding Color Blindness**:
- Color blindness is a condition where individuals have difficulty distinguishing between certain colors due to the malfunctioning of cone cells in the retina.

2. **Types of Cone Cells**:
- There are three types of cone cells in the human retina:
- **L Cone**: Detects long wavelengths (red and yellow).
- **M Cone**: Detects medium wavelengths (green).
- **S Cone**: Detects short wavelengths (blue).

3. **Normal Vision**:
- A person with normal vision uses all three types of cones effectively to distinguish a wide range of colors.

4. **Color Blindness Mechanism**:
- If one or more types of cone cells are non-functional or malfunctioning, it leads to color blindness. The most common form is red-green color blindness, where individuals cannot distinguish between red and green hues.

5. **Analyzing the Options**:
- The question provides four options:
- Red and Green
- Green and Blue
- Yellow and White
- Black and Yellow
- Since red-green color blindness is common, individuals with this condition struggle to differentiate between red and green colors.

6. **Conclusion**:
- The correct answer is that a color-blind person cannot distinguish between **red and green**.