reveal.js with custom css

reveal.Rmd

---
title: "Untitled"
output: 
  revealjs::revealjs_presentation:
    css: styles.css
---

## R Markdown

This is an R Markdown presentation. Markdown is a simple formatting syntax for authoring HTML, PDF,
and MS Word documents. For more details on using R Markdown see <http://rmarkdown.rstudio.com>.

When you click the **Knit** button a document will be generated that includes both content as 
well as the output of any embedded R code chunks within the document.

## Session Info

```{r}
options(width = 60)
sessionInfo()
```

styles.css

.reveal section p {
  color: blue;
}