Syntax highlighting in vim can be super tricky, by default a lot of desktop environments seem to have white terminals, which is a bit dumb as it’s easier to read white on black than black on white, as such the default vim syntax highlighting is often unreadable if you have a black terminal, giving blue comments on a black background and the like.
The fix for this is to set your vim background to dark, e.g.
set background=dark
You can either set this on a per session basis, but as I always use black terminals I’ve set this in my .vimrc file in my home directory.
Learning the vi And Vim Editors is a great book thoroughly covering both editors and the incredible power they contain. There’s a reason it’s been one of the most popular editors in the world since 1979!
If you’re in a hurry you can just do set bg=dark too