If you're remodeling a room and the new colours don't match the brick fireplace, painting the fireplace is an inexpensive upgrade that make a huge difference in modernizing your interior design. Make sure you buy around twice the amount of paint you'd think you'd need as porous brick will soak up a lot of paint.
Remodelling blog Young House Love recommends cleaning the brick first with a moist rag to remove any cobwebs or surface soot. If you have soot stains, you should use an oil-based primer to ensure the stains do not bleed through your paint. Then use a paint roller to apply two or three coats of flat or semi-gloss latex paint. You may need to use a paint brush to get the paint into deep grout crevices.
Make sure before you paint your fireplace that are sure about painting it and sure about the colour as paint is very difficult to remove from brick.
How to Paint a Brick Fireplace [Young House Love]