I will give a little tip of the cap to Behr for picking two entirely normal-looking, relatable, unattractive actors to play the couple in this ad. They are even the same race and of opposite sexes (can we even use the phrase "opposite sex" anymore? Well, I can. I'm a boomer. I can say anything I want.)
But I'm not going to let that "I thought you researched this" line go by. It's uncalled for- up until the moment it's uttered, this looks for all the world like a project these two decided to plan and carry out together. But the moment a mistake is pointed out, we the audience must be told that for some reason, it's the guy's fault. Picking out the best paint was HIS job- obviously, because it was done poorly. He promised to "research this," and he either didn't "research this" or he researched it badly. The brushes that were purchased are fine. The color is fine. Safe to assume that those were HER responsibility. The wrong brand of paint was selected. A mistake was made. They could have both made that mistake- but this is an American TV Commercial, and that means when a mistake is made, and there's a guy available to hold responsible, that guy is being held responsible.
There's really zero reason for the line. They could look at each other and say "we should have researched this" or "we screwed up." But we all knew that would NOT be the response. We all knew that this was going to be Doofus Schlub Husband's fault because it's the 21st Century and as a society we still have to pay the price for all those dumb sexist ads of the 1950s, 60s and 70s because eventually a certain number or wrongs will add up to a Right, I guess.