To create a shading color for the hex code #319179 (Swamp Green), we can generate a darker variant that can be used for depth and shadow effects. Here’s the updated color palette including the shade:

 <Frog Monster Theme>
1. Swamp Green - 
                            
                            #319179
                         - A vibrant green reminiscent of the swampy habitats where frogs thrive.
2. Swamp Green Shade - 
                            
                            #1E5B4D
                         - A darker shade of swamp green that adds depth and dimension, perfect for shading.
3. Mud Brown - 
                            
                            #4B3D27
                         - A deep, earthy brown that reflects the muddy grounds of a bog.
4. Lily Pad - 
                            
                            #A8D8B9
                         - A soft, light green that captures the essence of lily pads floating on water.
5. Monster Eye Yellow - 
                            
                            #E1C300
                         - A bright yellow that evokes the eerie shine of a frog monster's eyes.
6. Pond Water - 
                            
                            #2A6B7E
                         - A cool, dark blue that represents the mysterious depths of a pond.
7. Bug Bite Red - 
                            
                            #D94F3D
                         - A bold red that symbolizes a frog monster's appetite for insects.
8. Night Sky Purple - 
                            
                            #4A2C6D
                         - A deep purple that adds a hint of mystery and night-time ambiance to the palette.
9. Tongue Pink - 
                            
                            #D85E8B
                         - A bright, playful pink that adds a fun and slightly slimy look to the frog monster's tongue.

This darker shade of Swamp Green ( #1E5B4D ) can be used effectively for creating shadows on the frog monster’s skin, enhancing the overall dimensionality of the character.

Would you like to add more colors for highlights or other features, or need help with a specific design element?