Hmm, I had noticed that the blacks become red, but I didn't think of it as "wrong". Despite that, I find it useful enough -- it still removes much of the blue light and makes my eyes feel better.
I would love to know about any better Android apps like this, though.
Lux can do a better job, if you also install the Nexus 4 plugin from the same developer. Of course, you'll need a Nexus 4. If you don't have one it still does the same sort of transparent overlay.
I would love to know about any better Android apps like this, though.