r - different colors for each bar in stacked bar graph - base graphics

Question

I want to plot a stacked bar graph like the one attached, but I want the colors to vary between the categories aa, bb and cc. Specifically, I want the grey blocks in bb to be red and the grey blocks in cc to be green. The following code serves as a simple example and illustrates what I have already tried:

aa=c(0.2,0.6,0.1,0.1)
bb=c(0.4,0.5,0.05,0.05)
cc=c(0.5,0.25,0.1,0.15)
x=cbind(aa,bb,cc)
x #the data
aa   bb   cc

[1,] 0.2 0.40 0.50
[2,] 0.6 0.50 0.25
[3,] 0.1 0.05 0.10
[4,] 0.1 0.05 0.15

default behavior, all blocks have the same color in each categories

col=rep(c("white","grey"),2)
col
# [1] "white" "grey"  "white" "grey" 

barplot(x,col=col)

but I want the grey blocks in bb to be red and the grey blocks in cc to be green

col=cbind(rep(c("white","grey"),2),rep(c("white","red"),2),rep(c("white","green"),2))
col

[,1]    [,2]    [,3]   
[1,] "white" "white" "white"
[2,] "grey"  "red"   "green"
[3,] "white" "white" "white"
[4,] "grey"  "red"   "green"

barplot(x,col=col) #not working

col=c(rep(c("white","grey"),2),rep(c("white","red"),2),rep(c("white","green"),2))
col
[1] "white" "grey"  "white" "grey"  "white" "red"   "white" "red"   "white" "green" "white" "green"

barplot(x,col=col) #not working either

Many thanks for any suggestions.

Answer 1

This works by adding one coloured bar to the plot at a time:

# white bars 
barplot(x, col='white', axes=F, axisnames=F, yaxp=c(0,1,2), las=1)
cols=c('grey','red','green')

# add coloured bars
for (i in 1:ncol(x)){
    xx = x
    xx[,-i] <- NA
    colnames(xx)[-i] <- NA
    barplot(xx,col=c('white',cols[i]), add=T, axes=F) 
}