Question

How can I:

1. Set the fill colors in the boxplot below? I tried the argument “colour” but that failed.

2. Change the legend text from “0”, “1” to something else?

   require(ggplot2)
   ggplot(mtcars, aes(factor(cyl), mpg)) +
       geom_boxplot(aes(fill=factor(vs), colour=c("grey50", "white")))
   

Answer 1

Instead of the colour aesthetic, you want to adjust the fill aesthetic. You can handle both of your questions (and much more) by adjusting the scale:

ggplot(mtcars, aes(factor(cyl), mpg, fill = factor(vs))) + 
  geom_boxplot() +
  scale_fill_manual(name = "This is my title", values = c("pink", "green")
                    , labels = c("0" = "Foo", "1" = "Bar"))

The ggplot2 website help page for scale_manual is full of good examples.