I really like Funko's Hikari Groot toy. It's big and hefty, nearly 12" tall, has good proportions, and very nice detail work throughout. If you've considered getting a Funko Hikari figure, this is a great place to start. It's not "proper" Japanese Sofubi, despite what the box may say, but the quality is top notch.
I had to paint it, and went all getting three of the standard figure (which, again, looks really nice). I wanted something more colorful. Inspiration comes from Kenner's wild 1980's Swamp Thing toys. While I never had any as a kid (too scary!) they fascinated me then, and their bizzaro schemes are still a great place to start.
Using Monster Kolor, I sprayed both solid colors and metallics at different angles to highlight the details. Unusually for me, I skipped the pearl effects and high-gloss clearcoat. That leaves the constrast between the satiny solid greens and teals, and the glossy metallic red and green highlights. His eyes stand out with metallic yellow.
I had a great time getting into all the little details of the figure, and I hope you all enjoy it too!