Here's a harmonious color palette for a calendar featuring 3 distinct blues and 4 vibrant greens:

### Color Palette: Calendar Harmony

1. **Sky Blue**
   - **Hex Code:** 
                            
                            #87CEEB
                        
   - **Description:** A light and airy blue that evokes a feeling of openness and clarity, perfect for enhancing readability.

2. **Ocean Blue**
   - **Hex Code:** 
                            
                            #0077BE
                        
   - **Description:** A rich, medium blue that adds depth and sophistication, providing a strong contrast to lighter shades.

3. **Royal Blue**
   - **Hex Code:** 
                            
                            #003DA5
                        
   - **Description:** A deep blue that conveys reliability and stability, ideal for highlighting important dates.

4. **Mint Green**
   - **Hex Code:** 
                            
                            #98FF98
                        
   - **Description:** A soft and refreshing green that promotes a sense of calm and balance, perfect for a serene calendar layout.

5. **Lime Green**
   - **Hex Code:** 
                            
                            #32CD32
                        
   - **Description:** A bright and lively green that energizes the palette, making it suitable for marking festive or special events.

6. **Forest Green**
   - **Hex Code:** 
                            
                            #228B22
                        
   - **Description:** A dark and earthy green that provides a strong grounding element, useful for important reminders or notes.

7. **Teal Green**
   - **Hex Code:** 
                            
                            #008080
                        
   - **Description:** A unique blend of blue and green that ties the palette together, adding a touch of elegance and versatility.

### Summary
This palette features a balanced mix of blues and greens, ensuring that each color is distinct enough for easy differentiation while maintaining a cohesive look. The lighter shades can be used for background elements, while the darker tones can highlight key calendar events.