Blue points all appear in the lower right-hand quadrant in the plane formed by the first two principal components.
Is it a good interpretation of the biplot (right panel) to say that blue points are mainly characterized by large values of X1 and X2 and small values of X3?
PCA biplot
? $\endgroup$to say that blue points are mainly characterized by large values of X1 and X2 and small values of X3
Roughly saying, yes. When it comes to precise treatments of the distances on the plot much depends on the normalizations applied. If I find time today later I will perhaps write an answer. $\endgroup$