Method:
For the salmon, put paprika, garlic, oil, chili powder, thyme, allspice, 1/4 cup of the grapefruit juice (reserve remaining for salad dressing), salt and pepper into a bowl and stir to blend. Place the fillets on a plate and rub the spice mixture evenly over each fillet. Cover and refrigerate for 1 hour.
Preheat the grill to 375°F (or medium heat). Oil the grill and cook fillets, turning once, until just opaque in the center, about 4 minutes per side. Transfer to a plate and set aside.
For the salad, whisk together reserved grapefruit juice, oil, vinegar, ginger and agave nectar to make a dressing. In a large bowl, toss the greens with enough of the dressing to coat them, then divide the salad equally among 6 plates. Arrange grapefruit, papaya and avocado atop the greens and drizzle with remaining dressing. Transfer salmon to plates with salad, garnish with lime wedges and serve.