Now to the next part of your argument.In the true sense that there's nothing like the experience of color anywhere in the universe except in a brain, so too, and ironically, God doesn't exist anywhere in the universe except in a human brain. The brain that believes "color" exists "out there" while arguing that God doesn't, is living in an illusion from which it's incapable of freeing itself.
But wait, let me pause just a moment to note that in all you've posted so far, you have not yet answered your own question in the topic: why you are not an atheist. I'm not sure what you are doing, but you are not making an argument against atheism. And what the dickens is a "tautological oxymoron?" It would almost certainly have to be something that refers to itself to refute itself, like one of Epimenides paradoxes.
In any case, there is an immense difference between the perception of colour, and the perception of God. The difference is very simply this: one is the result of very real physics upon our perceptual aparatus -- and the other is not.