At the Pandoc user guide you can find that:
Pandoc will automatically highlight syntax in fenced code blocks that are marked with a language name. The Haskell library highlighting-kate is used for highlighting, which works in HTML, Docx, and LaTeX/PDF output. To see a list of language names that pandoc will recognize, type pandoc --list-highlight-languages.
The color scheme can be selected using the --highlight-style option. The default color scheme is pygments, which imitates the default color scheme used by the Python library pygments (though pygments is not actually used to do the highlighting). To see a list of highlight styles, type pandoc --list-highlight-styles.
To disable highlighting, use the --no-highlight option.
Your answer is right there, if I run
pandoc --list-highlight-styles I get:
Your question is for inline highlighting, but you should change for the three backticks syntax if you want customized code highlighting.