Error in annotating row names as data points in a PCA plot
Maybe try

plot(evecdat$PC1, evecdat$PC2, xlab="PC1", ylab="PC2", pch="24", cex.lab=2.5, cex.axis=1, type="n")  
text(evecdat$PC1, evecdat$PC2, evecdat$Sample, col=as.vector(evecdat$color))


This should plot the sample names as text (taken from the evecdat$Sample column), colored as specified in the evecdat$color column. See ?text for details.