1. Combine the canola oil and annatto seeds in a small saucepan. Bring to a slow simmer over medium heat and cook for 5 minutes. Turn off the heat and steep for 15 minutes.
2. Strain the oil into a Dutch oven or large heavy-bottomed pot with a lid; discard the seeds. Add the coriander and cumin and cook on medium heat for 2 minutes. Turn the heat to medium-high and add the chickpeas, mango, garlic, bell peppers and onions. Season liberally with salt and black pepper and cook until the onions and bell peppers are soft, 6 to 8 minutes.
3. Add the chicken stock and olive brine and bring to a boil. Add the rice, stir to combine and bring to a boil again. Lower the heat to medium-low, cover and cook until the rice is tender, 15 to 20 minutes. Fluff with a large fork and stir in the sliced olives. Adjust the seasoning with additional salt and black pepper if needed. Serve in a large bowl, or mound onto a serving platter.