R code used to produce the graph shown below.

barplot(c(2,5,6,3), col=myblue, 
        names.arg=c("Four", "shades", "of", "blue"), ylim=c(0, 6.5)) 
m <- matrix(c(2,5,6,3),2) 
barplot(m, col=c("lightgray", myblue), 
        names.arg=c("Group 1", "Group 2"))