Transformed color scale with nice guide in ggplot2

Transformed color scale.R

library(ggplot2)
library(scales)

# Generate data
myData <- data.frame(x = rnorm(1000),
                     y = rnorm(1000))
myData$z <- with(myData, x * y)

# Make an untransformed plot
badVersion <- ggplot(myData,
              aes(x = x, y = y, colour = z))
badVersion <- badVersion + geom_point()
print(badVersion)

# Make a custom transformation
norm_trans <- function(){
  trans_new('norm', function(x) pnorm(x), function(x) qnorm(x))
}

# Update plot with transformed color scale
badVersion + scale_colour_continuous(trans = 'norm'))