For the eye color of the frog monster, we can introduce a captivating and striking color that complements the existing palette. Here’s the addition:

 <Frog Monster Eye>
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.
10. Eye Green - 
                            
                            #A2D600
                         - A vivid and luminous green that adds a captivating pop to the frog monster’s eyes.

This new color, Eye Green ( #A2D600 ), enhances the whimsical and slightly eerie character of the frog monster, making its eyes stand out vibrantly.

Would you like to explore any other features, such as textures for the skin or patterns for the character’s body?