If dark surfaces absorb/store more light/energy than light surfaces, then does dark skin, on average, store energy from light most efficiently?
Melanin is a chemical compound(s) found in the skin and is responsible for skin pigmentation.  The darker the skin tone, the more melanin is present.  In light-toned-skin, melanin is produced as part of the tanning process when the skin is exposed to UV radiation.  Melanin is a very effective filter for UV radiation.  The more melanin present in the skin, the less light is available for light-catalyzed chemical processes that occur in the skin.

As Dissenter noted in his comment, light energy is not stored per se in the human body.  Rather light catalyzes certain reactions in the skin and the products of these reactions can be stored (at least for a while) for use in the body.

Vitamin D production is an example of an extremely important light-mediated process that begins in the skin.  Vitamin D is thought to play a role in a large number of regulatory processes throughout the body ranging from bone health to cancer.  Because melanin is such an effective filter of sunlight, non-white populations are at an increased risk of vitamin D deficiency.