AFAIK vimwiki's markdown syntax doesn't emphasize in any way blockquotes. I mean:
> This is a quote is presented instead as simple text. For reading notes it can be confusing. So, how do you highlight both the > and the quote?
You can modify the behavior of syntax files. Create a file at .vim/syntax/after/markdown.vim with the contents:
"highlight the entire block quote syn match Statement "^> .*" Note 'Statement' can be any highlight group. You can see a list of highlight groups with :so $VIMRUNTIME/syntax/hitest.vim)
>nor the whole block of text, @D.BenKnoblemarkdownBlockquoteinhttps://github.com/blueshirts/darcula/blob/master/colors/darcula.vim. It has only extra headers highlighting.