In a large pot place the cleaned mussels and pour 3/4 cup of boiling water into the pot. Cover and steam for about 3 minutes or until mussels open. Remove from heat and allow to cool. Transfer the mussels with a slotted spoon to a bowl, reserving the liquid, and strain the liquid through a fine sieve into another small bowl.
In a small bowl let the saffron soak in the wine for 15 minutes.
In a large heavy skillet cook the onion, the ham, and the bell peppers in the oil over moderate heat, stirring, until the vegetables are softened, add the garlic, and cook the mixture, stirring, for 30 seconds. Add the tomatoes and cook the mixture, stirring, for 5 minutes, or until it is thickened. Add the saffron mixture and the reserved mussel liquid and boil the mixture until most of the liquid is evaporated. Season the sauce with salt and pepper and let it cool to room temperature. While the sauce is cooling discard the top shell from each mussel and loosen the mussels from the bottom shells. Top the mussels with the sauce and arrange them on a platter.
Courtesy of Gourmet Magazine