AI is notoriously inconsistent with design advice.

What colors were historically used in 1930s Cape Cod homes? I’d research that and forget AI altogether.

edited to add this Google search partial results.

Neither blue looks good with their table and chairs. I don't know what color would look better, but I don't think any shade of blue would work.

I agree, the first blue, looks dark and dreary, the second blue, looks like it belongs in a baby nursery. If they want something bluish, maybe looks for a bluish green aqua in a lighter color. Not those awful blues that are in the pictures. Congratulations to them on their new home. The paint thats in there looks fresh. Maybe leave it for a while. Get moved in, and settled, and their furnishings in place, and then see what color might be the best , if they still want to paint.

on-line color consult ... ugh!

This forum can help, but there is no substitute for finding a local color consultant who can stand in the rooms that need to be pained ... and even then you might not end up really loving what someone else thinks you should put in your space!

Why the rush?

A few short years ago the trend was for gray, gray and more gray colors. They should live in the house, make furniture/fabric/rug decisions and then paint the rooms in complementary colors.

With no trim on the arches, the color transition from one room to another will have to be on an edge, so pay attention to how that will look if you have a dark color in one room next to a lighter color in adjoining room. This is probably the reason the sellers kept in all the same color.

Is the rug theirs'? If so the walls blue is overload. If the rug is theirs use the background color on the walls and the same on the trim in a different sheen

Just a suggestion on placing the table in the dining area.

Stillwater (Benjamin Moore) - it’s a deep blue - Might be an option.

The AI rendering of Delft is not very accurate. It actually has a bit of gray and green in it. My laundry cabinets are Delft

The table appears to be an oval in the provided pics so the diagonal table/chair layout will not work.

I second living there and finding a rug before painting. That may suggest some colors to pull from the rug for the walls.

A other vote for getting the floors (rugs) done first.

I also didn’t like the blue paint. If rooms are open to each other, such as the dining room and kitchen, the colors need to flow. If the walls aren’t covered with fingerprints, I would wait on painting them. Yes, it’s easier to paint an empty house. But it’s not fun to buy more paint after moving in because it looks wrong.