I wonder if it arose out of a shared human tendency to enjoy use of vivid colors? I cannot come up with another explanation... Why should a group of artists think that it's such a good idea to paint and represent form with colors that depict emotion?
Colors are important for humans.
I really like colors.
I really like colors.
I also really like the rain.
My favorite kind of weather involves pretty sunlit skies with rain drizzling... "How does that work?" you ask... Well, it can happen. It has happened in front of my eyes... You just need a partly cloudy day, and the clouds will shower rain, while sun shines through the rest of the sky, and there you have it. A beautiful, sunny, rainy day. Usually accompanied by rainbows in the sky...