Noah is a three-dimensional retelling of an apocalyptic Bible story, with a bit of patricide and hulking Ent-things thrown in. Oddly enough, even though it's purportedly about God taking vengeance on all of the people in the antediluvian world, the cast contains no actors of color. Huh.
When asked about this particular point by website The High Calling, co-screenwriter Ari Handel said this was on purpose — but, don't worry, guys, he totally thought long and hard about it:
From the beginning, we were concerned about casting, the issue of race. What we realized is that this story is functioning at the level of myth, and as a mythical story, the race of the individuals doesn't matter. They're supposed to be stand-ins for all people. Either you end up with a Bennetton ad or the crew of the Starship Enterprise.
OH, OKAY. Race doesn't matter; ergo, everyone's white. So post-racial. But, wait, never mind — Handel immediately admitted that it does actually matter. Digging himself way deeper, he continued:
You either try to put everything in there, which just calls attention to it, or you just say, "Let's make that not a factor, because we're trying to deal with everyman." Looking at this story through that kind of lens is the same as saying, "Would the ark float and is it big enough to get all the species in there?" That's irrelevant to the questions because the questions are operating on a different plane than that; they're operating on the mythical plane.
It's hard to fathom the amount of blind and ignorant privilege necessary to proclaim that it's somehow distracting to represent non-white people in a movie that's meant to depict the mythical origin of mankind. Also to just boldly and unabashedly proclaim that you see whiteness as integral to the construction of the "everyman." And, furthermore, it's just plain wrong — as Greta Christina points out at Free Thought Blogs, "there are, in fact, people who find mixed casts to be, you know, representative of humanity, and who find all-white casts distracting and weird."
In closing, a little pro-tip: if you, as a white person, reflect for a while on the issue of race and conclude that "race doesn't matter," then you probably need to reflect a bit more.