Delta[0] applies syntax highlighting to the code sections of git and diff output, and uses background colors (instead of +/-) to indicate added / removed content. It's written in Rust, and uses the same syntax highlighting library as bat[1]. In fact, any bat configuration that you already have in place (environment variables, custom themes/language support) is automatically honored by delta. Delta also infers and highlights substrings that differ between lines (similar to Github, Gitlab and other diff viewers) and removes visual clutter from Git and diff output.
[0] https://github.com/dandavison/delta
[1] http://github.com/sharkdp/bat/