About half the cars I see on the road are silver, gray, slate blue, or some other color that can be difficult to see even in good driving conditions. When it's foggy out, as it was Monday, Tuesday, and Wednesday mornings, your damn cars are invisible. And I should know: I drive a silver 2000 Honda Accord. My previous car was slate blue.
So for the love of god, TURN ON YOUR HEADLIGHTS. In foggy conditions, they're not to help you see. They're to make you visible to others.