I have to move, so I wanted to clean things up properly for the next owner.
Did the next owner fall in love with your existing paint color choices? Patch it, paint it, and get out if it doesn't lower the selling price.
Just make sure to actually do a good patch job. A bad patch job is wayyy more noticeable than any paint color discrepancy.
Kind of a dumb question but I couldn't find the answer anywhere, so I figured I'd ask here just to sanity check.
I won't judge =)
Say I have a drywall repair
The texture of the drywall repair alone is going to provide an obvious enough difference unless you're a professional patcher and feather the paint fairly wide.
that I need to paint over, and the previous owner of the house didn't leave a can of paint in this room's particular color, so I go try to get a gallon of matched paint somewhere, and it ends up not being a perfect match.
It almost never is a perfect match. Age changes paint in a way not reproduceable by simply color matching.
I've heard in this case you have to paint "corner to corner", which I assume just means painting the whole wall, and not necessarily the whole room.
Yes, paint the whole wall.
If that's the case, does this usually work out okay? Or is it often noticeable enough to where you need to paint the entire room?
Yes, it should work just fine.