Step 1
Go to the editing screen and on the left side, select the thumbnails of the slides that you wish to change colour. You do this by clicking the tick in the top right hand corner of each slide.
If you wish to change the background colour in all your slides, simply choose the 'select all' button on the yellow bar.
Step 2
Next, click on the 'Colour' button next to 'Select all' and choose your desired colour.
Step 3
The background colour for all selected slides has now been changed.
