Bring a large pot of salted water to a boil over high. Add pasta, and cook according to package directions for al dente. Drain pasta, reserving 1 cup cooking liquid.
Meanwhile, heat oil in a large skillet over medium-high. Add onion and garlic; cook, stirring often, until onion is softened, about 3 minutes. Add bell peppers and jalapeño; cook, stirring often, until peppers are crisp-tender, about 2 minutes. Stir in jerk seasoning. Add shrimp and coconut milk. Reduce heat to medium, and bring to a simmer. Cover and cook, stirring occasionally, until shrimp are just cooked though, about 3 minutes.
Uncover, and reduce heat to low. Add cooked pasta, and toss to combine, stirring in reserved pasta cooking liquid, ¼ cup at a time, as needed to thin sauce. Season with salt to taste. Divide pasta evenly among serving bowls; sprinkle with scallions and additional jerk seasoning. Serve hot.
