Your character doesn't know their Alignment
One of the things that causes a bit of head-shaking/scratching in D&D is "Alignment." The idea that a person or creature is definitively in a particular moral camp. This elf is Good, that orc is Evil, etc. What's more, there are even *kinds* of Good & Evil; "Chaotic" Good, "Neutral" Evil, etc. This can present problems in the realism department. It strains credibility sometimes that creatures and people are walking around with these "labels" hanging on the souls or auras or whatever; classifying them one way or the other.
Sometimes, as with Outsiders -demons, etc.- it makes sense that they fall into a particular category. It is a supernatural creature that is metaphysically aligned by definition one way or the other. People and sentient "natural" creatures, are a different issue.
A paladin is Lawful Good. Everyone knows that. If they don't act Lawful Good, they aren't paladins anymore and their horse won't talk to them, etc. Here's the thing; a paladin doesn't *know* he's "Lawful Good"; he knows he's RIGHT. He behaves according to the tenets of his faith and in harmony with the wishes of the divine forces that favor him. If he steps too far out of line, he loses that favor. The concept of "Lawful Good" is a player aid for understanding how to *roleplay* the character.
Likewise, a Neutral Evil assassin doesn't necessarily think of himself as "Evil." He obviously doesn't hold sentient life in high regard (other than perhaps his own), but he doesn't prance about humming Michael Jackson's "I'm Bad." Evil is about the ends, Good is about the means. Your typical assassin wants power and/or money. He's good at killing people and uses that skill towards his ends. That people have to die to further his goals doesn't bother him much. Better him than me, he thinks. He doesn't know he's Evil, he knows he's ahead of the game and that the other guy is cooling meat. Except in cases of the mentally ill, almost no one labels themselves "E-V-I-L." If an assassin started caring too much about the people he was killing, or feeling a great deal of remorse, he might well become an ineffective assassin and -in alignment terms- non-Evil.
Good/Evil is as Good/Evil does
Kobolds. You hate 'em, right? Hey, who doesn't? They're sneaky little scaly ugly critters that skulk around in the dark, steal whatever isn't nailed down, attack from ambush but run from a fair fight.They set up traps to skewer, crush, poison or otherwise mutilate you. They kill, they torture, they loot. They are B-A-D; horns to tails, scales to bones. Alignment in MM: Lawful Evil, right?
Wrong.
It says "Usually Lawful Evil." Same thing, right? Nope. It means that these little buggers are sentient creatures. Just like humans, elves, dwarves and so on. Typical Kobold culture/society is set up on a Lawful Evil model; i.e. the Strong rule the Weak. Order is essential for survival/success. No mercy to enemies, etc. etc. Not a nice place to live by our standards, but think about this:
Biggers. I hate 'em, don't you? 'Course you do! Huge, vicious loud giant spongy-looking brutes that come stomping into our nice quiet caves with their air-stealing, blinding fires. They'll try to pin you up against a wall and slaughter you where ya stand. We try to protect the nest, we dig deep, we post guards. The foolish biggers hardly even notice the "surprises" we leave for them until they've stepped in them. So Stupid! Sure we take from them what we can! But are we not the spawn of the great dragons? Does the noble blood of wyrms not flow in our veins? We are cunning, we are wise. We fight with our minds, not just our muscles. They come to foul and destroy the nest, to take the hoard! We fight for the glory of the nest, to protect the eggs and protect the hoard! Humans? Elves? Bah! The biggers are rotten to the core. Take it from me, they are BAD!
Now, that's a pretty simple profile of Kobold thinking. Not that most of them are mental giants or anything. However, in any situation where you're dealing with a group of individual minds, there are bound to be some that don't think like everyone else. I mean let's face it, adventurers have some pretty abnormal ideas about how to live/act/dress/behave by most folks' standards. Just as you can have a Chaotic Good drow and an Lawful Evil gnome, you might run across a Lawful Neutral or even Neutral Good Kobold. I mean, why not? They are smart enough to have tools, languages and spells for crying out loud, why not different morals?
Now, the life of a Good Kobold in an Evil Kobold tribe/nest would not be an easy one. The truth is, survival rates for such individuals would be low. But a Neutral or Lawful Neutral one could maybe get by. He might see the value of protecting the group and why it could be unwise to be soft on enemies, but he may also believe in a time for mercy, or kindness. He may feel that sometimes, just sometimes, it's better to save a life than to take it or let it end.
So, how do you know whether the kobold you're looking at is evil?
Well, if you are in the middle of a melee with the bugger, I doubt anyone will fault you for walloping it into paste. Even if combat hasn't started yet, having a little lizard-guy point a crossbow at you is justification for defending yourself with lethal force. So, in those cases, alignment is a secondary issue at best. Even a paladin would be on safe moral ground cutting a Good-aligned being in half if they attacked him in earnest. So what about non-combat situations?
Well, as a DM, I work under the idea that "Evil is as Evil does." What this means is that the way to know if something or someone is "Evil" is by its actions. To assume alignment by species when dealing with sentient non-Outsiders, while statistically a fairly safe bet, is morally no different than racism. For instance, Gnomes and Goblinoids feelings about each other are a lot like the Palestinians and the Israelis; they've got a lot of history of bloodying each other up and when it comes to the feud between them, none of the hats are white to all eyes. I'm not saying that a Good character would necessarily be "breaking alignment" by killing a kobold just because it was a kobold, but consistently acting in that way might eventually cause an alignment shift that reflects the character's obviously limited regard for the value of life. This is, of course, the point of this rambling:
Your alignment is a guide for roleplaying, not something the character itself is aware of. Therefore it changes to fit the character if the character doesn't fit it.
End of ramble.
