To highlight a bar in base R histogram, we need to understand the X-axis values and pass the col argument inside hist function appropriately. We just need to put a separate value for the bar that we want to highlight and set the colouring of the rest of the bars to 0 (that is default in base R). Check out the below examples to understand how it works.
> x<-rnorm(100) > hist(x,col = c(rep(0,5),4,rep(0,5)))
> y<-rnorm(1000) > hist(y,col = c(rep(0,3),4,rep(0,9)))