How paint can change a room

The difference was more clear before this image was reposted to hell and back and got all blurry

Light interacts with colors and paint and will refract more or less accordingly. Because our eyes work through light capture, that's how this concept works for us.

I might wage that unless you're in said room it will be harder to realize this effect.

I would also say that this only effects perception and I guess a windowless room will need a lot of artificial light (just a guess though).

Pretty much look the same to me too, wonder if it is different in person.

No differences, none at all.

Would paint everything white for more friendly atmosphere, would hate to sit in a dark cave. That's all I care about.

They are all the same, except that the color is different.

This is a marketing ploy by an interior decor site - it's just make-believe. Colors can't make things look bigger or smaller, as anyone who's seen colors knows.

Same here. The "stretching the space vertically" looks like it's elongated it horizontally to me.