Color matches are never exact duplicates of the previous color. To get an exact duplicate requires the label of the color match done previously. You can take a color sample and have it matched 3 times, and each time it will come out very slightly different. That's not that important when painting a whole room, but it does impact touchupss.

That's very interesting, though it was my understanding that SW wasn't just shooting off a color card or something when they made up the original paint color. They actually had a list that told them what the local company's formula would be in SW because they routinely make color matches of this company's paint colors. So I assumed it would be extremely close, if not a perfect match when they did another gallon of it. But while the original was a slight creamy white, the new base one was a gray-white.

Today they painted the entire ceiling in the area that included the spot needing touch-up, since touch-up was leaving a circle--and this time the painters had SW actually do a color match off an old paint card of the color so it would go with the rest of the ceilings and also because it's the color of our trim, but in a flat finish. It was much closer to the original white than the gallon they mixed using the color match formula, but enough different that they painted the whole area so the spot would blend in. They actually draped off everything and sprayed it because the painter was concerned that a roller wouldn't look as smooth.

I guess I can just be happy that we had a builder who just fixed it, rather than walk away from the problem. But it seems like others would run into this problem unless SW adjusts the formulae when they change their base.

For example when someone gets SW to do a color match of a BM color, doesn't SW have formulae for those BM colors (or at least many common ones) already in their computers rather than just using a card to try to color match? Maybe I'm all wrong with how they do color matches.

The only time I ever had a color match done by Sherwin-Williams they held the color card to a zapper of some sort and the computer did the rest.
It was a horrid match... not even close.
I should add that this was around 2006.

Even if they have the formula, you can't count on it coming out exactly right. I had some SW Nomadic Desert color matched at Lowes in Valspar paint (my painter preferred Valspar paint). First they used the formula they had in the computer. Nope, way off. Then they re-did it using the card I had gotten at SW. Nope, way off (but it did match the the one they did w/ the formula :) ). Luckily, my painter was good enough that he could tell them what to tweak to get a good match. I sure miss him (he moved out of state)!!!

Thanks everyone for the insight! I guess that explains the problem. And evidently it has a lot to do with what each company's base paint is to begin with. Fortunately, I love the color matches that SW did of this particular company--actually better than the original color samples--otherwise that would have been a nasty surprise.

I'm a real paint novice, and rarely paint a room myself, so I admire those of you who routinely tackle that. It's the cutting in that gets me. I have lots of a gray-blue paint I love leftover from the original painting and would love to do the halls in it, but have decided the other color will remain at least for a couple years because of cutting in around all the built-ins and trim. Thanks again!

I've been very fortunate with my local SW store being able to match paint. I had a sample of a dutchboy color that wasn't in their system. They scanned the painted sample and then mixed it. It was no where near close. They just kept tweaking it until it was a perfect match. Sometimes I think they get to busy or lazy to do a manual match but they can do it.

I have wondered if the paint dispensers aren't calibrated as often as they should be resulting in a couple extra drops of color ending up in the paint can.

We painted our kitchen ceiling about 8 years ago when we moved to our home. We needed to repaint some areas a couple of years ago when we remodeled, and I went to buy new ceiling paint. My dh suggested I take our old empty paint can with me. They had recently changed the formula to make it a brighter white. So thankfully they were able to tint it to the older ceiling paint formula. I would have never thought that would have been an issue, so thank goodness my dh considered it!