Selection Pressure on Orca Whale Coloration What is the proposed selection pressure that leads to the distinctive coloration of Orca whales? I can find nothing in the literature.

You can find a discussion of this topic in the literature:

Mitchell, Edward. 1970. Pigmentation pattern evolution in delphinid cetaceans: an essay in adaptive coloration. _Canadian journal of Zoology_ 48(4): 717-740.

Perrin, W.F., 1972. Color patterns of spinner porpoises (Stenella cf. S. longirostris) of the eastern Pacific and Hawaii, with comments on delphinid pigmentation. _Fish. Bull_ , 70(3), 983-1003

Caro, T., Beeman, K., Stankowich, T. and Whitehead, H., 2011. The functional significance of colouration in cetaceans. _Evolutionary Ecology_ , 25(6), pp.1231-1245. <

And related helpful article:

Evans, W.E., Yablokov, A.V. and Bowles, A.E., 1982. Geographic variation in the color pattern of killer whales (Orcinus orca). Report of the International Whaling Commission, 32, pp.687-694. <

I'll let you explore these and their citations.

Remember, Google Scholar is your friend.