I built this looking at a design I found online. It is very different from that version I looked at. Some of my changes were needed due to not having the parts. Afterward I took a look at the character from the show. That shows my colors are really wrong. Head and arms should be the lighter green. Legs should be darker green. Alas I don't have the pieces to do that at the moment.
After building I compared his size to Groot. To my surprise I managed to make him the same size.