If the House of Reps ballot papers are green, why are the Senate ones white and not red?
Thanks for your question Sarah.
The Senate ballot papers are white because it is harder to read text printed on red paper. The House of Representatives ballot paper is printed in a light green to distinguish it from the Senate ballot paper. This makes it simpler for voters to know which house they are voting for and which instructions to follow when filling out the ballot paper.
The different colours also mean that once voters complete the 2 ballot papers, it is easier to identify which ballot paper is to be placed in the ballot box marked House of Representatives and which one goes in the Senate ballot box. When officials from the Australian Electoral Commission empty the ballot boxes and begin to count the votes, they can easily see if any ballot papers have been mixed up.
Sample Senate ballot paper – voting above the line

Australian Electoral Commission
Description
This image is of a sample Senate ballot paper showing how to cast a valid vote above the line. There is a printed black horizontal line through the ballot paper. There are 7 boxes with 'Party' written above the line. These boxes have been numbered 1 to 6, one box has been left blank. There are many boxes with 'Surname, Given names, party' written below the line. All the boxes below the line have been left blank.
Permission should be sought from the Australian Electoral Commission (AEC) for third-party or commercial uses of this image. To contact the AEC email: media@aec.gov.au or phone: 13 23 26.