Not gonna lie, I kind of thought the skin looked generic at first glance. I can’t help but ask why was this even made? Because it doesn’t seem to be up to standards.
For the color aspect, I think the issue is that green doesn’t come across as a “true” dragon that people imagine. A lot of depictions of dragons in modern media often have their scales be devoid of much color, with the dragons being black, brown, etc. I figure it’s to try and make it blend in the world next to live action characters, and a green colored dragon would ruin the illusion that Harry Potter is battling a fire breathing dragon.
Think of it this way: Imagine you’re watching Harry Potter, The Witcher, Game of Thrones, etc., and you change all of the dragon’s colors to the same color of green that Dragoon Mercy has. Would that reduce the seriousness of the beings and atmosphere of the show? If not, would other colors such as yellow, pink, or even a rainbow colored dragon affect your impression of the creature or show?