Pat salmon fillets dry with paper towels and cut into 1.5-inch cubes. Chop bell peppers and onion into 1-inch pieces to match salmon size.
Mix smoked paprika, garlic powder, onion powder, sea salt, and black pepper in a small bowl. Whisk olive oil, lemon juice, and Dijon mustard separately until combined.
Thread salmon cubes and vegetables onto soaked wooden skewers, alternating pieces for even cooking. Thread approximately 4-5 salmon pieces per skewer with vegetables interspersed.
Brush the smoky tender grilled salmon skewers generously with oil-lemon mixture on all sides, then sprinkle spice blend evenly across each skewer. Reserve extra oil mixture for basting during cooking.
Preheat grill to medium-high heat (around 400°F). Lightly oil grill grates to prevent sticking and ensure beautiful sear marks.
Place skewers directly on grill and cook for 6-8 minutes per side, turning once halfway through. Baste with reserved oil-lemon mixture after flipping for maximum tenderness and flavor.
Salmon is done when it flakes easily with a fork and reaches 145°F internal temperature. Transfer to serving platter immediately and garnish with fresh dill and lemon wedges.