Google forms has moved to a new version of the application, however, the ability to change the background colour of the form itself hasn’t been carried over in this update. As a result there may be situations in which the old version of Google forms is required, for example for accessibility purposes.
In order to return to the old version of Google forms you need to use the question mark icon in the bottom right hand corner from within the forms editor, and use the button labelled ‘Back to the old forms’. This will take you to the old editor.
From within this editor you can do more extensive customisation of the forms layout and theme. In order to customise the theme you need to select the ‘Change theme’ option from the top tool bar.
This will bring up the theme options on the right hand side and you can select ‘Customize’ from below your theme of choice.
Once you have selected the customise options you can choose to change the background colour of the form from the options on the right hand side.