If you have a very cheap webcam. CCD noise is unavoidable (speckling of the pixels). Software with Frame averaging will improve things a little.

Having said that, your "low light" comment seems to indicate you have low light! You will be amazed at how bright a set has to be to avoid light problems. Notice that people on stage and on TV often sweat a lot!!! Good lighting is particularly relevant with webcams that have small lenses. Use as much light as you have, diffused through greaseproof paper etc to avoid shadows and strong reflections. You will know if you have too much as you start to white out and lose colour definition. It is difficult to over light with home equipment such as anglepoise lamps etc. The added advantage of strong lighting is that flicker is reduced.

Some lights can alter the true colour of objects. The white balance enables the user to adjust the colour balance of the image so a white object appears white in the captured image.