1. Earthy Green - 
                            
                            #5F9E5F
                         - A calming green hue inspired by nature and the environment.
2. Ocean Blue - 
                            
                            #0077BE
                         - A deep blue shade representing the vastness of the oceans and the importance of water conservation.
3. Sunshine Yellow - 
                            
                            #F9A602
                         - A vibrant yellow shade symbolizing the warmth of the sun and the energy of the Earth.
4. Rustic Brown - 
                            
                            #8B4513
                         - A warm, earthy brown tone that represents organic materials and sustainability.
5. Pure White - 
                            
                            #FFFFFF
                         - A crisp, clean white color that represents purity and the importance of protecting our planet. 

This color palette is perfect for an Earth Day social media poster, as it captures the essence of nature and the importance of preserving it. The combination of greens, blues, yellows, browns, and whites creates a harmonious blend of colors that will catch the eye and convey a positive message. Use this palette to create a stunning visual representation of your commitment to the environment and inspire others to do the same.