What is the term for a special layer that acts as a color filter for a single layer or for all the layers beneath it?

the truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey.

the answer to your question is tooth decay.