Love this idea that I recently spotted on Houzz. I see so many new construction homes with a similar set up--fireplace (meant to house a TV above) with built-in bookcases on each side.
Houzz
I often suggest painting the back of the bookcases for color, but painting just the mantel and fireplace surround is a great way to use a bold color without going overboard. (A dark color is also another way to make the TV less noticeable.)