This is the room in question. You can see the matte swatch on the wall.

That's flashing. (Google for more and better info) But basically the swatched spot absorbed the additional coats of paint and gloss differently. In other words, the swatch made the substrate (wall) uneven and so your final coats of paint look uneven and splotchy.

Only way to fix it is to sand it down and clean it up really well. I'd do the entire square inside the trim. And then repaint two even coats. Let the first coat dry out well.

To avoid the same thing from happening in the future, never test paint colors directly on the wall. Use the large paint chips from paint brands or paint peel and stick color sample decals. There are products like Samplize that will send you pre painted tester decals but we've found color accuracy discrepancies so I can't recommend them.

But Samplize is better than using paper or poster board to make your own sample; just check the Sampleize color carefully. Because anything that's a paper product absorbs paint - the colorant and gloss possibly at different rates of absorption (because it's paper) giving you a distorted view of the color.

I will look into this, BUT, I didn't cover the swatched part with additional layers of paint, I painted around it. Not sure if the paint looked less matte when I first swatched it and then became more matte over time, I didn't pay attention. It should be matte, but looks more eggshell right now.

I painted around it

lol! First time I've heard of anyone doing that. :) The sample was probably a different gloss level than the gallons.

It needs to be even and the same. I'd still knock it down with a light sanding, clean it up and apply two top coats.

I am putting a painting in that spot :)

The color is Hague Blue

Another pic

Gorgeous! Smart woman. 😅

Love the wall color!

hahah! Great solution.

I'd give the paint some time to cure, meanwhile, you might call Farrow and Ball and ask them the question. I'd be surprised if there was that much of an issue with their paint. Did you prime underneath the FB paint?