I’ve done a couple remodeling jobs lately on my own house and a rental house that we have. In both cases I knew exactly the color and luster of the paint but it is impossible to get the colors to match when you put them up.
There are several factors at play. First off, interior paint gets darker over time. If you match the colors in the mix, they’ll be lighter than what’s on the wall. Second, you can have fading and wear in certain areas. When you see the wall as a whole its not noticeable, but try to repaint only a portion and it will show right up. Third, the formulas for the base colors will change, especially when a company has reduced the amount of VOC.
So the real lesson is that its hard to touch up or match new paint to old paint. Better to assume that it won’t match and paint the entire wall to the edges or corners. Once you turn the corner you’ll no longer perceive it.