The optics of melanin absorption are far from simple. Melanin may appear as a particle - as in melanosomes or smaller particles as in the ink of cuddle fish - because it has a large index of refraction it will not only absorb strongly but will also scatter incident radiation. The aggregation state of the particles matters - as in melanophores in frogs that produce adaptive changes in coloration - and the type of monomer units in the macro molecule; some are fairly stable and others photolabile. Since melanin may not be considered a soluble substance it's concentration will vary within the cells as it does in human skin. So, it matters where it is located within the cell and its particular form. Not easy to answer in a few lines.