This isn't Colors-eligible, but one of my favorite theories from The Sims 2 is that the townie Olive Specter is a serial killer. She has a large graveyard in her lot, she spends her time sharpening sticks and collecting mushrooms, and there are a lot of clothes from her victims in her closet. She was married about 8 times and her husbands all befell mysterious "accidents", and she's implied to have had a child with the Grim Reaper. There's a lot of environmental storytelling details that (are honestly pretty overt, but still) make it fun to speculate.