Here’s a color palette for your modern note-taking app featuring black, blue, green, and pink, along with additional complementary colors to create a cohesive look:

### Color Palette: Modern Note-taking App

1. **Midnight Black**
   - **Hex Code:** 
                            
                            #000000
                        
   - **Description:** A deep, rich black that serves as a perfect background color, providing a sleek and modern feel while ensuring high contrast with other colors.

2. **Electric Blue**
   - **Hex Code:** 
                            
                            #007BFF
                        
   - **Description:** A vibrant and bold blue that adds energy to the design. This color is ideal for buttons and highlights, drawing attention without overwhelming the user.

3. **Emerald Green**
   - **Hex Code:** 
                            
                            #28A745
                        
   - **Description:** A fresh and lively green that symbolizes growth and creativity. This color can be used for success indicators or accents within the app.

4. **Blush Pink**
   - **Hex Code:** 
                            
                            #FF6F61
                        
   - **Description:** A soft yet striking pink that brings warmth and approachability to the app. It can be used for notifications or soft highlights.

5. **Cool Gray**
   - **Hex Code:** 
                            
                            #6C757D
                        
   - **Description:** A neutral gray that pairs well with the bolder colors. It can be used for text and secondary buttons, providing a modern touch without distracting from the main colors.

6. **Bright White**
   - **Hex Code:** 
                            
                            #FFFFFF
                        
   - **Description:** A clean and crisp white that enhances readability and allows the other colors to pop. This is perfect for text and backgrounds when a light theme is needed.

### Summary
This palette combines boldness and warmth, creating an inviting and modern aesthetic for your note-taking app. The colors work harmoniously together, allowing for clear navigation and an enjoyable user experience.