You can change the background of your question slides to a different solid or gradient color to increase contrast between the background and text of a question slide.
By selecting the solid color fill, you apply a plain, even color style to the quiz background.
To specify a solid fill color:
As you pick a color, the preview pane in the upper-right corner will show both the old and the new colors. The new color will be automatically applied to the background in the preview area. If you want to roll back to the old color, just click it in the preview pane (Current) or click the Cancel button.
To apply the changes only to the current question slide and close the dialog box, click Close. To apply changes to all existing and new questions, click the Apply to All button.
Using the gradient fill style is helpful when you want to set up an attractive background where one color changes to another across the question slide.
You can swap the colors by clicking the Swap colors option.