Hardboiled eggs can last up to a week in the fridge. Be sure to label and date the eggs. They are likely spoiled if they are older and should be tossed. If the yolk is gray or watery, the egg is probably wrong. If the shell is slimy, it’s contaminated with bacteria or mold. A brown shell is a sign of spoiled eggs.
A hardboiled egg’s color is a good indicator of how fresh it is. A pale, greenish-blue yolk means that the egg has been overcooked.