two ggplot and colour=x question

Hi

I am using ggplot with the aesthetic=list(..., colour=x, ...)

ggplot()
ggline()

I have four different values in x ("ren", "cyn", "mixed", "bare") and I 
have two questions

1) I would like to assign specific colours to the values, i.e. green, 
red, blue and brown. How can I do this? I did not understand 
map_colour_brewer.

2) I don't want the legend top be plot. How can I disable the legend to 
be plotted?

Thanks

Rainer

Rainer M. Krug, Dipl. Phys. (Germany), MSc Conservation
Biology (UCT)

Department of Conservation Ecology and Entomology
University of Stellenbosch
Matieland 7602
South Africa

Tel:		+27 - (0)72 808 2975 (w)
Fax:		+27 - (0)86 516 2782
Fax:		+27 - (0)21 808 3304 (w)
Cell:		+27 - (0)83 9479 042

email:	RKrug at sun.ac.za
       	Rainer at krugs.de