VIM colors downloader in Python
Very nice code in general! Here are a few points, though:

Think about using os.makedirs instead of os.mkdir. The former allows creating nested directories (so os.makedirs("~/long/new/path") will create all other folders in betweetn as well, if needed).

You should never have a bare except. This prevents you to e.g. CTRL-C to abort the program, since it will also be caught. Use at least except Exception, which all normal exceptions inherit from (but not some special exceptions like pressing CTRL-C).

In general it is usually not the best idea to have a lot of string addition. You could use format instead in repo_formatter:

def repo_formatter(scheme):
    base_url = scheme['github_repo']['address'].replace('github.com', 'raw.githubusercontent.com')
    return '{}/master/colors/{}.vim'.format(base_url, scheme['name'])


You have some very obvious comments in your code, especially in download. Comments should explain why you do something and not what. The latter should be obvious from your code! And in that function it is really easy to follow what happens, because you have chosen appropriate variable names :)