Season the chicken legs with salt and pepper. In a large skillet, cook the annato seeds in the olive oil over moderate heat until the oil is a deep brick red, about 5 minutes.
Strain the annato oil into a 9-by-13-inch baking dish. Add the carrot juice, vinegar, bay leaves, thyme, garlic and chiles. Add the chicken and turn to coat. Refrigerate for 6 hours or overnight.
Preheat the oven to 375°. Preheat a grill pan. Grill the chicken in the grill pan over moderate heat for 4 minutes, turning once. Transfer to a rimmed baking sheet and cook for 30 minutes, or until the juices run clear.