Dear R-list

I'm trying to get each regression line, plotted using abline, to be of a different colour as the following code illustrates.  I'm hoping there is a simple indexing solution.  Many thanks.

## code from here
colours=c("black","red","blue","green","pink")
Mean=500;Sd=10;NosSites=5;Xaxis=seq(1,5,1)
SlopeCoefficient=5;Site=(gl(NosSites,length(Xaxis),labels=1:NosSites))
Predictor=rep(Xaxis,NosSites)
InterceptAdjustment=rnorm(n=NosSites,mean=Xaxis,sd=50)
RandomIntercept=rep(InterceptAdjustment,each=length(Xaxis))
PreResponse=rnorm(n=length(Predictor), mean=Mean+SlopeCoefficient*1:length(Xaxis),sd=Sd)
Response1=PreResponse+RandomIntercept

#create data frame
Data2=data.frame(Site,Predictor,Mean,SlopeCoefficient,RandomIntercept,Response1)
Data1=data.frame("Site"=Data2$Site,"Predictor"=Data2$Predictor,"Response1"=Data2$Response1)
#plotting
var=as.numeric(levels(Data1$Site))
par(mfrow=c(1,3))
plot(Response1~Predictor,data=Data1,xlim=c(min(Xaxis),max(Xaxis)),ylim=c(MN,MX),
     pch=as.numeric(Site),main="Raw data with linear regresssions by Site")
by(Data1,Data1$Site,function(Site){
  par(new=T)
  abline(lm(Response1~Predictor,data=Site),col=colours[])#index in here.
})
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