[R] Help with color coded bar graph

[Luis Naver]

I have a list of observations that are -1, 1 or 0.  I would like to  
represent them in a horizontal bar color coded based on value like a  
stacked bar graph. I can achieve this in the form of a png with the  
following code:

A = floor(runif(10)*3) - 1

png(width=100, height=10)
par(mar=c(0,0,0,0))
image(matrix(A), col=grey(c(0.1, 0.5, 0.9)))
dev.off()

However I would like to do this with one of the standard plotting  
tools (i.e. barplot) to take advantage of labels and multiple  
series.  Any help would be appreciated.

- Luis Naver