You could ‘css hack’ it:
Create a new style, call it highlight-text, then in one its field (for example the background image), paste this: }.psc-highlight-text::first-line { background-color: blue;}{ (replace blue by whatever color you need/want)
Now, add the highlight-text class to your input field on your button’s actionPerformed event script to enable the effect, and remove it + delete the text when you get your new data.
edit:
You can also put that css bit, without the first and last brackets, in a custom theme file. You’ll still need to create the style class. Make sure the names match, with the psc- prefix in your css selector.