The wall is almost certainly already some variation of Swiss coffee, which is like a drop of black and two drops of umber per gallon… juuuuust enough to give it a little color.

When I used to help people pick colors the primary advice I gave them was that once it’s on the wall you will never see the difference between the four shades of [color] you’re looking at because at scale your brain blends it in with the lighting and ambient color of the rest of the room.

Sheen makes more of a difference, and the answer is always satin/eggshell for living spaces and gloss for kitchens and bathrooms (because it’s more moisture resistant and washable). Flat can go fuck itself, it only exists as a cheap option for track homes who don’t care about your paint looking good for more than six months.

Source: worked at a paint store for several years, did a loooot of color matching by eye.