R Markdown also comes with several built-in syntax highlighting styles. Supported styles include default, tango, pygments, kate, monochrome, espresso, zenburn, haddock, breezedark, and textmate. Pass null to prevent syntax highlighting. To use a highlighter for a single .html file output from a .Rmd file, you edit your YAML:

title: "README.Rmd"
output_format: 
  html_document:
    highlighter: tango

My render script

And here is the script to generate the highlighters:

purrr::walk(
  .x = as.list(rmarkdown:::highlighters()),
  ~ rmarkdown::render(
    "input/single.Rmd",
    output_file = glue::glue("{.}.html"),
    output_dir = "gallery/highlighters/",
    output_options = list(
      toc = TRUE, 
      toc_float = TRUE,
      theme = "cosmo",
      code_download = TRUE,
      highlight = .x
    ),
    params = list(dynamictitle = glue::glue("Texas Housing Prices: `{.}` highlighter"))
  )
)