there are a few problems with your suggestion:
1. Impersonating. With colours such as the darker blue, people could change their profile to match admins. This could be funny, but it would cause many rather bad situations. For that matter, impersonating is not allowed. I think this suggestion would only stimulate to do so, hence I'm against
2. The 'million roles' problem. If you want to change your colour in discord, you'll have to make a new role for each of these colours. This means that there will be a lot of unnecessary roles. I don't think these are helpful at all.
3. Developing time. To only make VIP levels (and maybe java ranks as well) be able to change their roles, they would have to make a new or install a current bot that can do so. This would obviously take time, which I don't think is worth it at all.
4. General confusion. People would see you with a green name, and the first thing the chat would say is something like 'huh, I didn't know you played on java and have an emerald rank'. This is unnecessary confusion that is caused.
If you count up all the negatives and put them next to the positive point your name looks better in another colour, ill have to vote disagree. Hope you understand!