I'm not even kidding or anything here. I can always tell whether a person is going to be a friend, enemy, or just kinda there. I can also tell when people are sad but pretending to be happy, and am 75% right when it comes to people "liking" me or not. I used to think this was normal and everyone could do it.
Leaving aside for a moment the whole colors bit, and, admittedly, playing the devil's advocate, I am most skeptical of this statement for two reasons. Firstly, when it comes to testing a theory, humans have a bad habit of remembering what validates it and forgetting what refutes it. Take, for example, the weatherman, who have a reputation in any town for being wrong. Their atmospheric predictions could be very often correct, but if the were right, well, that's good, it rained when they said, there was sun, there was snow, not exciting. But when they're wrong, it's often a big deal: there was a thunderstorm when they said it was pure sun; the "snowstorm" left a light dusting, and no more. They get a few days wrong, and most people remember it. As people talk to each other, they recall the failures, reinforce each other's position, and thus, a faulty theory is "proven" true.
This tends to get worse when it comes to supernatural powers. For a while, I was under the impression that I could affect electricity, because so many streetlights went out when I passed under them. Then (after a statistics class on this topic) I counted, for a week, the number of streetlights I passed, and the number that went out. Numerically speaking, the one light that went out was more likely to be coincidence, compared to the two hundred or so that didn't. It's also why people with self-confessed "abilities" tend to be shot down by "skeptics" regardless of their validity. The person with powers remembers all the times it worked; the skeptics remember all the times it didn't. They both follow the human inclination to remember significant events, and neither can convince the other of their validity.
Secondly, assume that the statement I quoted from you is completely true, that you are right about intention, that your statistics are accurate, that there are no lapses in memory. First impressions color (pardon the pun) our interactions with others for as long as we know them. If the first time I meet someone, they glare at me, I'm probably not going to try and make friends. If they give me a cookie, I'm not likely to blow them off. What your statement says is, basically, you go by first impressions alone. I mean, have you tried being friends with several people with "enemy" or "just there" auras (more than three, at least) and they've all come up null? Have you ignored someone with a "friend" aura, and had them become buddies anyway? Have you fallen out with anyone, let bygones be bygones, or reached out to a stranger? And has it always failed?
Long story short, there are a number of factors about your ability that don't sit right. I'm not denying that you can see colors, or that they're auras. I don't think you're crazy. I do ask that you take a step back, and try to remember the outliers, the times when it didn't work. If you can't think of any, ask others. And, even though you know you're right, try not to go solely off first impressions, aura or otherwise.