Brushing teeth 3 times a day and still yellow and smelly?

Bacteria: Brushing your teeth will help, however the yellowness can be due to tartar build up and need to be cleaned by hygienist smelliness can be due to bacteria on the tongue, use a tongue scraper and rinse with otc product.

Oral hygiene: The color of teeth depends upon the integrity of the enamel(outer surface) if the enamel is more transluscent, the teeth will appear more yellow .The smell could be from the bacteria that lives under the gum between the teeth. That is why regular professional cleanings are necessary and flossing every 24 hours is required to prevent bacterial growth(and odor). Brush the surface of the tongue too!