plotPCA legend

[FrAoJm]

Hi!!

I am using the "plotPCA" function from this package but I would like to add a legen to the PCA plot, but I am having some difficulties doing it. I am using an S4 SeqExpressionSet where the columns are the samples (GSMXXXXXX) and the rows are the gene IDs. The phenoData is a matrix having the same samples in rows and the condition in one of the columns.

I would like to have a legend indicating what colour corresponds to each condition to make the PCA understandable.

Is that possible?
Thanks!