r - Coloring boxplot outlier points in ggplot2?

Question

How can I color the outlier points in ggplot2? I want them to be the same color as the boxplot itself. colour= is not enough to do this.

Example:

p <- ggplot(mtcars, aes(factor(cyl), mpg))
p + geom_boxplot(aes(colour=factor(cyl)))

I want to color the outliers by factor(cyl) as well. This does not work:

> p <- ggplot(mtcars, aes(factor(cyl), mpg))
> p + geom_boxplot(aes(colour=factor(cyl), outlier.colour=factor(cyl)))

Answer 1

Update (2015-03-31): see @tarch's solution for ggplot2 >= 1.0.0

solution for ggplot2 <= 0.9.3 is below.

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As @koshke said, having the outliers colored like the lines of the box (not the fill color) is now easily possible by setting outlier.colour = NULL:

p <- ggplot(mtcars, aes(x=factor(cyl), y=mpg, col=factor(cyl)))
p + geom_boxplot(outlier.colour = NULL)

• outlier.colour must be written with "ou"
• outlier.colour must be outside aes ()

I'm posting this as a late answer because I find myself looking this up again and again and I posted it also for the related question Boxplot, how to match outliers' color to fill aesthetics?