You can change the color of your topic background on a topic-by-topic basis or in your style sheet. This procedure is for changing individual topics.
From Format, click Styles.
If the Hide inherited styles check box is selected, remove the check mark to see all styles in the Styles list.
From Available in, select the topic name (not the style sheet name).
From Styles, select Background + Text, and click Modify.
Click the Format button and select Borders and Shading. The Borders and Shading dialog opens.
Click the Shading tab.
Under Fill, select the color you want to apply to the background.
Click OK until you return to the Styles dialog, then click Close.