So I guess I'm either a dictionary-definition agnostic or a wishy-washy atheist.

There's no reason you can't be both. Agnosticism is an epistemological position, and atheism an ontological one. One can admit that absolute objective knowledge is impossible, but still conclude that, within said limits of knowledge, that something does not exist. People rarely feel compelled to qualify themselves as agnostic towards the tooth fairy or the proverbial invisible purple unicorns. An agnostic atheist simple places gods among the very large set of things for which there is no evidence, and thus can be assumed not to be.

(There's a larger epistemological problem revolving around belief in something that operates independent of, and can alter, the basic criteria for knowledge, but I'll save that for later.)

That's part of the point; being invisible, it can't have a color, therefore it can't exist.

Yeah, that was the reference, but I shouldn't be faulted for forgetting the color of something that's invisible.