Diptych with the Virgin and Child and Three Donors

Diptych with the Virgin and Child and Three Donors
by Master of the Legend of St. Ursula
1486
Oil on oak panels, 28 x 21 cm
Koninklijk Museum voor Schone Kunsten, Antwerp

Can someone explain to me why baby Jesus is so often depicted with a red 'fro? (See previous post, for example.)

Here Jesus kind of looks like a cheap doll whose limbs are poorly stuck in his sockets, though the donors on the right don't seem to mind.