In Figure 1, we see that Population 2 from Northern Europe has a lot more different skin color alleles compared to Population 1 from equatorial Africa. This means there is more variety in skin color among people in Northern Europe.
A few reasons for this could be natural selection, where certain traits are favored, mutations, moving between populations, and other genetic changes over time. In equatorial Africa, the lower variety in skin color might be because having darker skin is better for protecting against the strong sun.