It will be easy to disregard number one as obviously, a guinea pig with black fur and a guinea pig with white fur will not make some a cartoonish guinea pig. The black fur is obviously a dominant trait which means that it will appear more often than the white fur.
This means that if the guinea pig is going to have 4 offspring, it is very likely that they will have black fur. Take note that this may change depending on the number of offspring that the guinea pigs will have. The more offspring, the better the possibility that there will be guinea pigs with white fur as well.