The solution does not contain lead iodide #"PbI"_2#. Typically, you would mix together a solution of lead nitrate #"Pb(NO"_3)_2#, which is colorless, and another solution such as potassium iodide #"KI"#, which is also colorless. Both compounds are soluble in water. When they are mixed, a double replacement chemical reaction occurs, in which the lead and potassium ions switch partners to form soluble potassium iodide #"KCl"#, and #"PbI"_2"#, which is a yellow solid that precipitates out of solution because it is insoluble in water.
