That statement is true, as far as it goes. Microevolution, of which variation in skin color is an excellent example, is variation that results from favorable combinations of existing genes. But for that to happen, the genes have to exist in the first place. Evolution depends upon mutations that produce genes with new, useful genetic information. Mutations don t create new, useful information.
Mutations cause information to be lost.
Our second conclusion is that mutations cannot be the origin of more complex organisms. Mutations can cause a species to devolve, but not evolve. Our whole thesis is that science depends upon observation. Beliefs that are not supported by observation, and are actually contradicted by observation, are not scientific. Deduction is not as reliable as observation.