To create a text frame thumbnail, go to the Art menu and click on the text frame icon. On the text frame thumbnail, you can edit text and add background art. Combine the text frame thumbnail with other thumbnails on the timeline. Click the text frame thumbnail and enter editing mode. Directly add text into “Enter text”. From the settings tray, click the background and change the background of the thumbnail. Hover your cursor over each image to preview the different backgrounds. Click to select.

Changing the color
Change the color of the background by adding an effect to the thumbnail. While editing the text frame, go to Effect menu and click on the Color Change effect (3rd from the left). Go to the settings tray and change the color.

Related items
Adding effects to your thumbnail
Combining text and thumbnails on the timeline