In mid to late fall, I love our Southern California Black Walnuts where they co-exist with the (evergreen) Toyon. The Walnuts are turning a bright, golden yellow and making an exquisite companion to the green leaves and red berries of the Toyon. Notice this combination when you drive the canyons, especially in the Santa Monicas. ---But if the question is about favorite "winter" tree, then give me those wonderful Chinese magnolias who finally drop all those burnt brown leaves (ugh), revealing silvery trunks and stems, soon to be decorated with either white star shaped flowers (Magnolia stellata), or pink, white, or purple cup shaped flowers (M. soulangiana).