Paint codes alone are so worthwhile. My current house has three light greys in it that are all subtly different and when I moved in there was just one grey paint can in the basement with no indication which one of them it was.
Source: this happened to my mom and she ended up with slightly discolored spot that people always assumed was a reflected light source.
Each major line of paints has slightly different colors, so figuring out of it was Sherwin Williams, Behr, Valspar, etc let me identify the right color collection and narrow things down enough for me to guess what he was using.
A chip as in a sample of the drywall... that I've found to be much more of a mixed bag. My last "matched" paint was nowhere close once the sun was shining on it.