Is it possible that the cross between two black Guinea pigs in puberty square a would not produce a white guniea pig?

Yes, it is possible for a cross between two black guinea pigs to produce offspring that are not white. If both black guinea pigs carry recessive genes for coat color, such as the gene for white fur, there is a chance their offspring could inherit those genes and be white. However, if both parents are homozygous for the black coat color, all offspring will be black. Thus, the outcome depends on the specific genetic makeup of the parent guinea pigs.