I've just found some deep frozen salmon in my freezer but I'm unsure if it's still eatable though the package says it still should. The case is that the salmon is still pink as it should be but it's back where the back bone should be, it's green/grayish. Is the fish still alright?
If you bought your salmon frozen, and kept it frozen this entire time then it is safe to eat.
Foods actually remain safe indefinitely when stored below freezing. You should be aware that safe does not necessarily mean palatable. As food ages, even when frozen, it degrades in quality via oxidation and other chemical processes. This degradation in quality will definitely affect the taste, and even the nutritional value to a degree.
For salmon, it will taste best within 7 to 9 months.