epslatex clustered histogram fills and patterns

Dear All,

I am having a bit of a problem with epslatex and a clustered
histogram. I have included a minimal example of my code at the end of
this post. If I use aquaterm for this I get a the clustered bars in
different shades just fine. However, in the epslatex terminal I only
get the first bar of each cluster shaded (the others appear invisible
when I compile my LaTeX do***ent). I have tried with patterns and
variations on calling the epslatex terminal and get the same result.

Clearly, I must be doing something wrong, but I'm not sure exactly
what. Perhaps someone could point me in the right direction as copious
Googling has so far not managed to assist. I would very much
appreciate any help.

Toby.

#set terminal aqua
set terminal epslatex
set output "monthly.tex"

set boxwidth 0.9 relative
set style data histograms
set style histogram clustered
set xlabel "Month"

plot 	'monthly.dat' using 2 fs solid 0.33 lt-1,\
		'' using 3:xticlabels(1) fs solid 0.66 lt-1

PS - if it is relevant I am using the graphicx and xcolor packages in
my LaTeX do***ent.