Beginning of a Highlighted paragraph- how to cancel it?

Apple has placed menu items for Highlight, and Comment on the Insert menu. That highlight, is not a proper word processing highlight, but rather a comment coloration. If this is what you have done, then click on the colored text, and when the popup occurs, there is a delete in the lower left corner of it.

The proper highlight is hidden in the Pages Advanced Options menu (The gear icon on the bold, italic, underline button row). It is named Character Fill Color. If you want to undo highlighted text applied from this source, you click in the inkwell, and in the lower-right corner of the popup, you will see the transparent selection. When you apply transparency, your proper highlight disappears. One can fine tune their color choice by clicking on the color globle instead of the inkwell.

And as if to make things even more interesting, Apple has placed a Background Color inkwell on the Format > Text > Layout tab panel. This sets the background color from margin to margin for selected text. A good way to make a paragraph block standout. Color reversal is performed by selection of the block of text, and applying transparency from the Background Color inkwell.