In recent years, Martin Stevens, Sami Merilaita, Roger Hanlon and dozens of other biologists have turned to empirical investigations of the appearance of animals, and especially what is commonly called "adaptive coloration" or natural camouflage.
Hanlon (at the Marine Biology Laboratory at Woods Hole MA) and his associates have focused on the extraordinary capabilities of cephalopods (octopus, squid and cuttlefish), which can rapidly change their appearance in complex, amazing ways—producing disguises beyond belief. There's a wonderful NOVA program about this research called Kings of Camouflage.
In the meantime, Stevens and Merilaita (biologists at the University of Cambridge and Abo Akademi University, respectively) have edited an anthology of recent studies related to this, titled Animal Camouflage: Mechanisms and Function (UK: Cambridge University Press, 2011). ISBN 978-0-521-15257-0. In the volume, there are seventeen papers on the widest range of aspects of adaptive coloration. It amounts to a fascinating survey of a rapidly expanding research area. As the only non-scientist to be represented, I was delighted to see the inclusion of my essay on "Nature's Artistry: Abbott H. Thayer's assertions about camouflage in art, war and nature."