Color Palette for Duplex Building Exterior:

1. Midnight Slate
   - Hex Code: 
                            
                            #1C1B1A
                        
   - Palette Description: This deep, dark gray shade is reminiscent of a moonlit night, adding a sophisticated and mysterious touch to the building's exterior.

2. Ivory Cream
   - Hex Code: 
                            
                            #FDF8F3
                        
   - Palette Description: This soft and creamy off-white color provides a clean and elegant look, creating a sense of sophistication and elegance for the building's exterior.

3. Rustic Terracotta
   - Hex Code: 
                            
                            #C46236
                        
   - Palette Description: This warm, earthy orange-brown hue adds depth and character to the building's exterior, giving it a rustic and welcoming feel.

4. Coastal Blue
   - Hex Code: 
                            
                            #2A4B7C
                        
   - Palette Description: This rich and deep blue shade evokes a sense of calmness and tranquility, reminiscent of the coastal waters. It brings a touch of serenity to the duplex building's exterior.

5. Forest Green
   - Hex Code: 
                            
                            #29582C
                        
   - Palette Description: This deep, lush green color represents natural beauty and harmony. It adds a refreshing and vibrant touch to the building's exterior, connecting it with its surroundings.

Note: These five colors can be used together to create a harmonious and visually appealing color palette for the duplex building's exterior.