This small study (N=98) did not find any effect on skin tone in a sample of US Mexicans. Sample size seems sufficiently to find a moderate effect, but cannot rule out a small effect. How large effect size would you estimate that skin tone plays in attractiveness ratings? E.g. r=0.2?
Good stuff. Although one could argue that it's not the skin color but the facial features or hair/eye color that make a population more attractive than the other. Anyway, good call! It's not a bad idea to include empirical studies looking at the relationship between race-typical physical variables and attractiveness. There are many studies showing an association in the expected direction. http://en.metapedia.org/wiki/Race_and_physical_attractiveness#Skin_color_and_facial_studies