It seems to be common practice to display the sell button first across various trading platforms and we have also received a number of comments from experienced traders that we should display sell first.
Would you care to share these comments? Would help to understand the rationale for having the sell button first as it doesn't provide any additional functionality.
On the two financial trading platforms I use, one has the buy button first and the other the sell button first. I don't have any preference in the order they are displayed.
Regarding the colours, I would suggest that could be changed as part of a complete refresh to the entire interface (desktop version) to make it less 'cartoonish' and improve UX.
Won't add any comments on that here as you've specifically requested feedback on button order and colour!