"thin sheet of metal," late 14c., from O.Fr. fueille "leaf," from L. folia "leaves," pl. (mistaken for fem. sing.) of folium "leaf" (see folio). The sense of "one who enhances another by contrast" (1580s) is from the practice of backing a gem with metal foil to make it shine better.
I like the idea that "foliage" is related to the idea of contrasts. And with that in mind, here are a few photos of the yellow maple leaves hiding in among the redwood branches at my house:
I hope you are having a peaceful, happy Autumn day.