Tilapia, like most fish, can change color when frozen. Freezing can damage the flesh of the fish, causing it to change texture and color. However, the extent of the color change can vary depending on a number of factors such as how the fish was handled before and after freezing, how long it was frozen, and how it was thawed.
In some cases, frozen tilapia can turn a slightly grayish or brownish color, which can be an indication of freezer burn. This occurs when ice crystals form on the surface of the fish, causing dehydration and oxidation. Freezer-burned fish can have a dry, tough texture and a slightly off taste, but it is still safe to eat.
If you notice any significant changes in the color or texture of frozen tilapia, it’s best to use your best judgment and evaluate the quality of the fish. If it looks and smells off, it’s probably best to discard it.