The 1E3 paper is difficult to type because, as previously mentioned here, and thanks to the work of Rein, a member of the Australian Stampboards Forum; there are three types of 1E3 papers. For some of the 'cents' values, the color change is enough evidence to know that the paper is 1E3.
The 15c Small Format Cattle changed to a lighter blue in 1939.
The 20c Martin Guemes changed to a darker blue in 1939.