R code used to produce the graph shown below.

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