I think it makes more sense for the "bad questions" column to be red, and the "meh questions" to be blue.
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The off-topic question box is blue, rather than red, because those questions are not "bad questions." In fact, they are meant to be quite useful in determining what is or isn't on-topic on the site (whether they are effective at that is another question). It's the "not a good example" questions that we don't want, hence why they give -2 reputation. By making the off-topic box red, you'll just make it even more confusing and less intuitive (if that's even possible) for the new users.
I agree with you that the classification is confusing, but I don't think that's the way.