Alexander Wang is usually in a slouchy white shirt with black pants or shorts.
Karl Lagerfeld and his tailored black suit and high, white collars.
Tom Ford is always in a variation of black suit. Sometimes he will shock with a white one.
It has been proven after you had become a successful designer in the fashion industry you have to wear the same or similar outfits all the times that your photographed. I guess it's an undying rule. I've never heard why this is true or not, but it really interests me as to why it's true.
Another thing that I've notice is that designers rarely wear pieces from their lines. I recently did an article were the girls from Rodarte explained as to why they don't. Maybe these facts and many others have been answered in their bios.