How can you tell when fish is done cooking and ready to serve? Do you go by color?

To tell when fish is done we must consider many variables of fish cookery. What type of fish is to be used, the type of cut, dressed, fillets etc., the weight & thickness of, and the type of cooking method to be employed. Seafood is one of the most often and easiest products to overcook. As a chef there are several species that I feel should be cooked only to medium rare; ie; Tuna and Salmon. In the homes of many people, though this would probably not go over with the family dining as a whole. You mentioned color yes, and this method of checking to see if the flesh is opaque throughout is by far the most recognized by home cooks and a good standard. Internal temperature of a stuffed or whole fish is a good way to determine doneness in some species. White spots start to appear on the top, coagulation of fluids forced to surface as the flesh contracts during cooking process. You need to determine your temperature preference of the fish to be cooked. When following a recipe, follow exactly in its entirety. Allow for carryover cooking. You can cook fish a little more but never less once completed.