In article ,
JohnP wrote:

I want to have a different coloured wall when I decorate the lounge.

20 x 12 feet

window & patio on one long side
fireplace & TV on one short side
doorway to hall other long side

I feel inclined to have the contrast and slightly darker wall as the long
side facing the window.

When we had our porch built, by an absolute jewel of a builder, he
suggested that when we painted the inside walls, we should not choose
white (which I had been thinking about): the porch would stick out like
a sore thumb: a darker colour would merge the porch into the house
better. He was absolutely right (we chose a dark salmon sort of
colour[1], which I had mixed at the Dulux counter).

J.

[1] Doubt if that would work for your long room wall, but it works
perfectly for our small porch at the front of the house.