Epub putting text in a blue box

Hi there,

I am working on an epub in ID CC. The author wants some text to be in a blue box and a different colour. I have worked out how to do this by putting the text in a new text box and making the background blue, and also applying a style to make the text white.

However, when the textbox exports to epub, it remains a fixed size and does not look good.

Can text boxes be exported to epub so that they resize, the way you can get images to do?

Or do I need to apply a css style to a div in the epub when I do the final edit in DW instead?

Thanks so much.