Ok update. I finished the first coat of paint - rolling and cutting. It came out great. I still need to do a second coat to cover up the underlying paint though. Is it easy to do a second coat of flat paint? What I mean is does the fact that I am using flat paint affect how the second layer of paint will go on? The first coat went on like butter, but given that I had some trouble painting the ceiling in flat (behr ceiling flat), I am hesitant to try the second coat of SW paint on the walls. Im still debating how I should approach fixing the cut in line. I did creep up into the ceiling slightly but my lines were not consistent. I am wondering if I should use an artist brush to create that straight line illusion.

Ugh, I'm dealing with this exact issue now. I've just spent the last two weeks stripping, sanding, priming my entire kitchen, plus painting 3 coats on the door fronts. I used some paint I had from last year when I painted the cabinet that covers up my electrical panel since I loved the color and had most of a gallon leftover. Well, I finished the doors and moved onto painting the cabinet boxes, but only had about a quarter can left, so I took the can in and asked them to give me another gallon of the same thing. Got it home and instantly realized it was not the same color, even though the label was correct, as were the labeled amounts of the colorants. The color I used on the doors was a nice creamy soft white, and the color they gave me was a stark white. I almost suspect they didn't put any of the tint in. So before I used it, I took it back to the store and told them about my dilemma and, long story short, they told me to use the paint as it is, and let it dry properly and they should be the same, and if not they'd see what they could do. Well three coats and two days later, it still looks quite different to me. I think I will just do a final coat in my original color, and hope for the best. It worries me, though, that I won't have any paint left for touch-ups. And of course I don't want to have to re-paint the doors again. Frustrating!

So funny timing on this because as said a couple years ago, I never fixed the tables, the WE touch up paint was garbage and then my trim paint was a pretty close match which did the job for a while. but I’m actually about to refinish these tables this weekend.... four years later. I since bought a little device that computes paint matches, and determined that the tables are a pretty close match to SW marshmallow or SW shell white. I haven’t used it yet, but the device tends to be accurate so good luck!

If I paint the entire board with new paint, will it be noticeable if it does It match 100% with the other 3? Odds are in your favor that no one will notice because color constancy wall to wall is inconsistent - just the nature of inherent light. If possible, carefully pop off the whole board you have to touchup and take it to the store so they can color match it right there. (don't' worry they've seen crazier than a whole piece of trim) Also easier to paint when it's off and then just reinstall.