Do I need primer before I paint a patch of my wall?

An electrician did some work at my house and she needed to cut a couple holes in the wall. The holes are repaired with two coats of “mud” (that’s what she called it) and have been sanded smooth. Now they just need to be painted to match the wall color. Do I need to use primer first, or can I just put the color right over the patch? The area in question is about 4 inches by 8 inches.