For the chermoula: Combine the saffron and hot water in a small bowl and let sit for 10 minutes to bloom. Heat the canola oil in a small saute pan over medium heat. Add the garlic and cook for 30 seconds. Cook the ancho, coriander, cumin and chile de arbol for 1 minute. Add the saffron and its soaking water. Remove from the heat.
Whisk together the olive oil, lemon zest, lemon juice and garlic-saffron mixture in a medium bowl. Mix in the bell peppers, tomatoes, mint leaves and cilantro. Cover the bowl and let sit at room temperature for at least 30 minutes to allow the flavors to meld, or refrigerate overnight. Bring to room temperature before serving.
For the grilled white fish: Heat a charcoal grill for direct grilling at medium-high heat. Brush both sides of the halibut with the canola oil and sprinkle with salt and pepper. Grill the halibut until golden brown and charred on both sides and cooked to medium or well done, about 10 minutes each side.
Carefully transfer the halibut to a platter and top with the chermoula immediately. Let the halibut rest for 5 minutes before serving, to allow flavors to sink in.