ggthemr包

library(ggthemr) ## devtools::install_github('cttobin/ggthemr')
ggthemr("light")

mtcars %>%
  mutate(cyl = factor(cyl)) %>%
  ggplot(aes(x = mpg, fill = cyl, colour = cyl)) +
  geom_density(alpha = 0.75) +
  labs(fill = "Cylinders", colour = "Cylinders", x = "MPG", y = "Density") +
  legend_top()
ggthemr_reset()