Say a woman has a cold. She and her partner want to have sex. Is he more likely to catch her cold from kissing her or from cunnilingus?
You know, there is a website for nearly every topic you can imagine: http://www.commoncold.org/understand.htm
To answer your question, the common rhinoviruses which cause the symptoms we know as a cold (which have many different serovars and are therefore classified as distinct clades of viruses, hence why we have not and will likely never “cure the common cold”) accrue on the adenoid glands (part of the tonsils) where they stimulate an immune response, hence the swelling of the throat and production of mucus, which causes runny nose and sneezing which helps to transfer the virus by using the infected victim as a vector.
I saw a video about a cold virus experiment on a college campus where they intentionally infected several volunteers and sent them out onto the campus to convince as many people as possible to kiss them on the lips, then checked back a few days later to see if the kissers caught a cold. Out of literally dozens of kisses, not a single person caught the virus.
So that suggests that kissing on the lips has a very low transmission rate.
I don’t have any similar data regarding cunnilingus.
Viruses tend to attack certain kinds of cells. The viruses that cause colds attack the cells lining the respiratory tract, so that’s where they are. That doesn’t mean there are none anywhere else, of course. They can get spread around by any number of mechanical means, and they’ll survive in any moist environment. A woman who’s had a cold for some time will no doubt have transferred some of the viral particles all over herself, including the outer folds of her labia.
Since the part of the body that tends to come in most contact with every other, including secretions from the respiratory tract, is the hands, it is from the hands that it is generally believed you are most likely to get viruses from someone else.
But if you touched an infected woman only on the lips and the vagina, then I would say you are less likely to get a cold from the latter.