R help - Nov 2011 - A question:How to plot hierarchical clustering with different colors?

Dear experts,

I would like to plot a hierarchical clustering of 300 items. I had a  
distance matrix with dimension of 300*300. The 300 items were from 7  
groups which I would like to label with 7 different colours in the plot.
> h<-hclust(as.dist(300_distance_matrix))
> plot(h,hang=-1,cex=0.5, col="blue")
I used the above script to plot the result. The cluster was all blue,  
the 300 item names were all displayed blue. When I tried to specify  
the seven different colours, I found there was no option to get the  
names to be displayed in different colours.

When I used graph and Rgraphviz packages, I could define a attribute  
list to specify the different group colours and plot a colourful  
graph. Is there any options in hierarchical clustering to do the same?  
Could someone kindly help me with this problem? Thanks in advance.


Sincerely
Yan