[R] Colors and legend on a scatterplot?

[buczkowski@delta.sggw.waw.pl]

Hello

I am new to R and I cannot overcome the 2 problems

1.Defining my own color scale for a value on a scatterplot
2.Adding legend showing values for colours

I have a set of points in area of my research with coordinates X and Y and
a value which I would like to show with colors.
 
#values for points are residuals from regression

stepmod = step(wmodzad, direction="both")

#I am adding residuals to original data to get coordinates for residuals

expzad = cbind(zadrz, residuals(stepmod))

#I want to have colors for classes defined as standard deviation from mean


std = sd(residuals(stepmod))
mn = mean(residuals(stepmod))
sdclas = seq(-3*std+mn, 3*std+mn, by=std)

#I would like to have colors from green to red, but I can't do it so I am
doing only

palette( rainbow(6) )

#I am dividing residuals into earlier defined classes by

residsd = cut(residuals(stepmod), sdclas, labels=FALSE) 

#or by (THEN POINTS DON'T APPEAR ON PLOT IN NEXT STEP)

residsd = cut(residuals(stepmod), sdclas)

# I am creating a plot

plot(expzad$X,zadrz$Y,col=residsd, pch=15 )

# I would like to add legend to plot showing values for colours from plot
but I can't do this. Simply help for 'legend' on my level of knowledge on
R is not helpfull.

loc = locator(1)
legend(loc$x, loc$y, legend = levels(residsd) )

Thanks in advance for your help

Rafal Buczkowski