[R] Customizing plot

[Mahmood Naderan-Tahan]

Hi,
1- How can I assign different  colors to different observations in the PCA chart? Assume, I have 10  observations and I want to use black color for the first 5 and read for  the next 5 observations.

Currently, I use 

 res.pca = PCA(mydata[,1:37], scale.unit=TRUE, graph=T)
 plot(res.pca,axes=c(1,2))


 
2- How can I change the plot area size and font sizes? With these commands
 
 dev.new(width=20, height=4)
 plot(res.pca,axes=c(1,2))

 The final plot is not what I expected. Please see the picture at https://imgur.com/UINTnv7 
 


     
 
 Regards,
 Mahmood