To see all of the editing options and features, click "edit" in a lesson box.
One of the buttons on the toolbar will be a highlighted "ab". After typing your text, highlight it with your cursor and then click the highlight icon. This will highlight the text the color that is under the "ab".
To change the highlighting color, click the black drop down arrow.
And then chose the color you wish to use for highlighting.
If you set the recurrence to save "weekly, going forward," all of your boxes in that position with that text will appear with the highlighting.