

They are, indeed, very, very blue.
According to the literature, the birch trees are painted with a water-based non-toxic pigment that will naturally wear off in time. The purpose is to raise social awareness for deforestation occurring on a global level.
While I'm not entirely sure how bright blue trees will stop the cutting of global forests, I can say that the baby was in dirt heaven.
Grubby?
yes.
Blue?
yes.
Indeed, our work here is done.