1. Stir the chili powder, garlic powder, onion powder, sugar, cumin, white pepper and paprika in a small bowl. Reserve 1 1/2 tablespoons mixture for the dressing. Sprinkle the salmon with the remaining seasoning mixture. Cover the salmon and refrigerate for 6 hours.
2. Lightly oil the grill rack. Heat the grill to high. Brush the salmon with 1 tablespoon oil. Grill for 8 minutes or until the salmon flakes easily when tested with a fork.
3. Beat the vegetable juice, vinegar, tomato, remaining oil and reserved seasoning mixture in a large bowl with a fork or whisk until blended. Add the salad greens and toss to coat.
4. Divide the salad among 6 plates. Top with the salmon.