It really depends on the severity of the cold. If you're just "getting over it", going with the suggestion by n_palum seems reasonable, a simple thing like telling them you'd shake their hand, but not today, that you're just getting over a cold. It informs them that you were sick, and you are managing now and are concerned for their own welfare.
If you're still actively in the middle of it hard, sneezing, coughing, difficultly talking/swallowing water, etc. I'd simply call the interviewer and tell them "hey, I hate to do this, but can we re-schedule the interview, I'm really not feeling well and don't want to give the wrong impression nor make anyone sick."
Any reasonable company/interviewer should gladly reschedule the interview for you; if not, from personal experience, I'd walk away.