He studied at the University of Belgrade"s Law School until 1940.
Kolak joined the Communist Party of Yugoslavia in 1941 thus becoming a Yugoslav Partisan. After that he was spokesman in the Ministry of Finance of the Government of SFR Yugoslavia and spokesman of the President of Yugoslavia, Josip Broz Tito. From 1963 to 1965 he was Vice President of the Executive Council of Social Research Bosnia and Herzegovina and became President of the Executive Council of Social Research Bosnia and Herzegovina in 1965 and held that post until 1967.
After that he was Vice President of the Federal Government of SFR Yugoslavia from 1967 to 1969 and President of the Yugoslav Chamber of Commerce from 1969 to 1974.
After the war, Kolak held various posts: he was Secretary of the People"s Assembly of Socialist Republic of Bosnia and Herzegovina, President of People"s Assembly in Banja Luka, President of the Supervisory Committee, and Minister in the Government of the Socialist Republic of Bosnia and Herzegovina.
Later he became a member of the Central Committee of the Communist Party of Yugoslavia.