Here’s a color palette specifically designed for your Gantt chart to distinguish each of your four projects while keeping the red for progress:

 < Project Color Palette >
1. Project Blue - 
                            
                            #007BFF
                         - A vibrant blue that represents stability and trust, perfect for a project that requires clear visibility.
2. Project Green - 
                            
                            #28A745
                         - A fresh green symbolizing growth and success, ideal for highlighting a project that is thriving.
3. Project Orange - 
                            
                            #FF7E00
                         - A bright orange that conveys enthusiasm and creativity, suitable for a project that encourages innovation.
4. Project Purple - 
                            
                            #6F42C1
                         - A rich purple that signifies ambition and luxury, fitting for a high-priority project.

This color palette ensures that each project is easily distinguishable while maintaining a professional look in your Gantt chart.

Would you like any additional colors for sub-projects or milestones? Or do you need further assistance with your Gantt chart design?