Banded cartridges were used for DCRA matches from 1921 to 1940 as follows
Year Bands Colour
1921 1 Rosanaline red
1922 1 Malachite green
1923 1 Gentian violet
1924 1 Victoria blue
1925 6 Rosanaline red
1926 6 Malachite green
1927 6 Gentian violet
1928 6 Victoria blue
1929 3 Rosanaline red
1930 3 Malachite green
1931 3 Gentian violet
1932 3 Victoria blue
1933 4 Rosanaline red
1934 4 Malachite green
1935 4 Gentian violet
1936 4 Victoria blue
1937 2 Rosanaline red
1938 2 Malachite green
1939 2 Gentian violet
1940 2 Victoria blue
In general, cartridges produced one year were assigned for the match of the following year. When insufficient quantities were held form the previous year, current production was chosen to make up the amount required.
Thus you could expect to see a 1936 head stamp with 2 red bands for the 1937 match, but you could also find a 1937 head stamp for the same match.
In short, the band code is for the year of the DCRA match, and cartridge headstamps may vary.
In addition, Cartridges head stamped 44 with one green band were made for the 1945 match. Also, 44 head stamps with one wide violet band were made for the late 1940's, the exact year unknown. 1945 cases were loaded with a nickel primer for the 1950 match.
Dominion Arsenals produced a special Olympics match round in 1948 using ball cases dated 1940-1943. These rounds were completely black to identify them.
The info here was taken from "Canada and the .303 British" by C.R. MacDonald