Here is a color palette tailored for a website focused on volunteering to plant trees, emphasizing nature, growth, and community:

 <Tree Planting Initiative>
1. Forest Green - 
                            
                            #228B22
                         - A rich and vibrant green that symbolizes growth, nature, and the lush foliage of trees.
2. Earth Brown - 
                            
                            #8B4513
                         - A warm, earthy brown representing the soil and foundation necessary for planting and nurturing trees.
3. Sky Blue - 
                            
                            #87CEEB
                         - A soft, calming blue that evokes the sky and open spaces, promoting a sense of peace and community.
4. Sunlight Yellow - 
                            
                            #FFD700
                         - A bright, cheerful yellow that conveys optimism and positivity, reminiscent of sunlight filtering through leaves.
5. Leafy Green - 
                            
                            #9ACD32
                         - A fresh and lively green that represents new growth, vitality, and the hope of a greener future.

This palette aims to create an inviting and encouraging atmosphere for users interested in volunteering for tree planting initiatives. The colors reflect the natural environment, invoke feelings of community engagement, and promote a sustainable message.

What kind of features or sections will your website include? This can help refine the design further!