Skin patterns and colors do have impacts on survivability! Some species use camouflage to avoid predation, others use bright coloration to attract mates. There

Skin patterns and colors do have impacts on survivability! Some species use camouflage to avoid predation, others use bright coloration to attract mates. There's also a flaw in your premise -- reproduction is not random, it's subject to selection at a number of levels. Most selective forces act to reduce genetic diversity, both at the selected gene, and at nearby genes.