Before the pros paint walls, they fill holes and patch cracks with joint compound. But if you paint directly over it, the compound will suck the moisture out of the paint, giving it a flat, dull look (a problem called “flashing”). Those spots will look noticeably different than the rest of the wall. To avoid that, pros prime the walls before painting.

Instead of using white primer, pros usually have it tinted gray or a color that’s similar to the finish paint. Tinted primer does a better job of covering the existing paint color than plain primer, so your finish coat will be more vibrant and may require fewer coats. This is especially true with colors like red or orange, which could require three or more coats without a primer.