...is like a gem turning in the sun. How you perceive it, depends on what aspect makes the greatest impression on you. The angle of the light, the brightness, the richness of the color, the motion, etc.
It's the same for almost anything you can name. Our opinions of things depend greatly on our first impressions. On what facet first caught our eye.
When I was a kid, my dad did two things a lot: smoke and travel. When he returned from a business trip, I remember hearing him come down the apartment hall from the elevators, and rushing to meet him, burying my face in the tobacco-smelling folds of his topcoat. So the smell of cigarette smoke will always equate with dad, home, love. The Surgeon General be damned.