The colours were taken from the arms. These colours were not fixed.
Various sources give different designs, but two main sets can be compiled.
This is not dated, but to judge from the font face used, it is from the 1920s or 1930s. It contains a sheet with the honorary flags of the governors of the provinces, adopted by Order in Council of 28 October 1936. It includes a construction sheet. The flags are 150x150 cm. Each stripe is 50 cm.