If using wooden / bamboo skewers, soak them in water for about 10 minutes before grilling. This will prevent them from burning on the hot grill.
Prep your grill. It's a good idea to use high heat (400 F or higher). The shrimp will be most tender and juicy if cooked very fast over very high heat.
Make salsa: Combine pineapple, bell peppers, rice vinegar, cilantro and 1/4 tsp lime zest. Season the salsa with a pinch of salt and refrigerate until ready to serve.
Thread shrimp through skewers.
Divide sweet chili sauce, placing 1/4 cup of sauce in each of two small bowls. Whisk in 1/8 tsp lime zest into each bowl. Set one bowl aside.
Just before grilling, pat shrimp dry with paper towels. Season on both sides with salt and pepper. Place shrimp skewers over the hottest part of the grill, turning them to get grill marks on both sides, until pink and cooked through, 2 to 4 minutes total. In the last minute of cooking, use one bowl of sweet chili sauce to liberally brush both sides of the shrimp skewers. (The sauce should start to caramelize and blacken in spots on the hot grill, so watch closely to prevent burning.)
When shrimp are cooked through, transfer to a serving platter and brush with the remaining bowl of sweet chili sauce.
Serve shrimp and pineapple salsa over rice, other grains, or to top salads.