It's my opinion that 1939 and 1940 were definitely gold. 1941 was blue. 1942 (???), 1944 and 1945 were definitely yellow. The helmets in the Cleveland papers for 39 and 40 had a shiny appearance. So I would go with gold for those two seasons. The helmets after the 1943 layoff were yellow. The youtube newsreel from the 1944 game at the Bears would indicate a definite yellow as does the 1945 NFL Title Game newsreel as well as pics from the Plain Dealer.
1942 gold (but NOT definite)