I would carry a white bag any time of the year if it matched my outfit. I could see a white bag on a white parka in winter. The only thing I would consider when carrying a white bag is whether it is a winter style bag. I would not carry a white straw bag in winter, but I would carry a satchel, hobo, duffel bag, etc
whenever i think about the "no white after labor day" rule, i always think of that movie Serial Mom, with Kathleen Turner and Ricki Lake. .... and how she killed some woman becuase she was wearing white shoes after labor day. chill Kathy, its not that serious. LOL
also, i dont agree with it either. as long as you look good, who cares what time of year it is!!
I used to have a canvas white (that was the color, it was leather, not canvas) MBMJ bag which I used during the winter. I don't know if I would use something stark white though, it might look a little summery.