if(!require("devtools")) install.packages("devtools")
devtools::install_github("briandconnelly/lato") 

library(ggplot2)
library(lato)

p1 <- ggplot(mtcars, aes(wt, mpg, color = as.factor(cyl) )) +
    facet_grid(cyl ~ .) +
    geom_line() +
    geom_point() +
    scale_color_hue(name = "# Cylinders") +
    labs(
        x = "Weight (tons)",
        y = "Fuel Efficiency (mpg)",
        title = "Just Buy a Convertible",
        subtitle = "Lighter cars are more efficient. Shave off some weight by\nditching the roof, and drive your savings to the bank!",
        caption = "Source: Motor Trend"
    ) +
    theme_lato()

p1

p1 + theme_lato_dark()