Whether I'm doing camera work or alarm work, I never offer or promise to touch up paint. I explain that small holes, if visible will be patched with joint compound, but the customer would be responsible for touch up painting, either by DIY or by hiring a trade person specific to the repair.
Many years ago, during a residential alarm installation, I drilled into a door jamb for a contact and hit a drywall nail that popped a chunk of drywall out of a wall painted in green. Patching this with joint compound left a good size white spot on a green wall. I hadn't discussed who would be responsible for touch up paint. So, I took the chunk of wall to the paint store, color matched it, and bought the minimum quantity, one gallon, required at the time. I touched up the wall and the customer was quite happy.
After that I made it a point to discuss, in advance of the install, or in advance of placement of a device when it might be necessary to remove a few sections to route wiring. If the customer balks at that, I find another path for the wire. Usually, the customer wants a device in a certain location and they agree that they would see to the repair of the drywall to their liking.
I'm not a drywall installer, with tape and texture experience, or a painter. If you take on that job and the customer doesn't like the outcome, you'll have some problems. If it's substantial repair, leave it to those who do it routinely.