Beginning in 2015.3, you can now turn on a Style Override Highlighter button on the upper right corner of the Paragraph Styles and/or Character Styles panels. It appears in a bright aqua color. In the illustration below, italic formatting was added on top of a paragraph style.
Here's the rest of that article: http://indesignsecrets.com/indesign-cc-2015-3-update-brings-bug-fixes-small-improvements.p hp
I would recommend never to work with style overrides, as it causes always problems.
But you can turn it on/off in ther right upper corner with the [+]-symbol.
Thanks so much. That worked. The reason I don't want the highlight on right now is because I'm designing a book cover and trying out a bunch of different looks. The blue highlight gets in the way of judging the design and the fonts. Once I've settled on a design, I'll set up the paragraph styles.