This is certainly the time of year for colds and flu. As others have indicated, following one's own common sense and inner urges are an important part of the whole experience of being in "yoga" or wholeness.
In general, during a cold or time of illness, rejuvenating and relaxing practices are indicated to provide the body a chance to recover. These practices help to put the mind/body into a relaxation mode which supports the immune system. As previously noted, chest opening on support may help to increase the flow of fluids and move the cold. Neti or water snuffing may also help.
During the winter the weather may be colder, so when we are well a more heating practice (Surya Namaskar) can be used to keep the body in balance and stimulate the metabolism.
As for foods, milk and rice are considered to be mucus producing. You may find other recommendations in an ayurvedic diet to supplement your asana practice.
Hope this if helpful.
Namaste - Chandra