Combine the vegetables and the anchovies in small batches and chop to a near-puree in a food processor, using the oyster water to help things along.
Combine this green slurry and the rest of the oyster water in a saucepan and cook over low heat, stirring every now and then, until the excess water is gone but the greens remain very moist. Add sugar, catsup, salt, cayenne, Worcestershire sauce, bitters and food coloring.
Make a blond roux with the butter and flour. Blend well into the greens, until the sauce takes on a different, lighter texture. Then mix in the bread crumbs.
Place large, fresh oysters into oyster shells, small ovenproof ramekins, or small au gratin dishes. Top each oyster with a generous tablespoon of sauce (or more, if you like). Bake 15 minutes in a preheated 450-degree oven, or until the top of the sauce has barely begun to brown. Serve immediately.