What can cause gray specks in saliva?

From saliva, throat?: Saliva shouldn't have anything in it. It should be clear and colorless. Some people get crystals in a saliva duct. People can get saliva gland infections, leading to pus or cloudy stuff in the saliva. "specks" from foods can get stuck in throat mucous, as well as dust mixed in with nose mucus that drips onto the throat to become throat mucus, and can mix with saliva to look odd. A dr can evaluate.

Fillings?: If you have some silver fillings in your mouth they may be breaking down or you could be grinding your teeth. Many people grind while they sleep and are having some time of stressful situation in their life at the time. You may also have a salivary stone that is breaking apart in one of your major glands. A dentist can confirm that with an x-ray if it is detectable.

Heavy metals: Maybe your amalgam fillings are falling apart?