Ever since I was a child walking in a field of sunflowers or passing them by in a car, I loved the way these flowers turned their heads to follow the sun. Also, the yellow of the leaves and the contrast with the head and seeds were supremely beautiful.
The Russian-born artist Wassily Kandinsky comments in his slim volume Concerning the Spiritual in Art on the opposition between yellow and blue and the movement inherent in them. He says that yellow moves towards the spectator and has a "parallel in the human energy which assails every obstacle blindly, and bursts forth aimlessly in every direction," while blue retreats, adds depth, and creates a sense of rest.
Surprisingly, Kandinsky adds that while blue has "the power of profound meaning," yellow is "the typically earthly color" that "can never have profound meaning."
What Kandinsky calls "the first antithesis" is actually the opposition between yellow as the quintessential warm color and blue as the benchmark cold color. It's an opposition that appears in treatises on color far and wide.