On 06/03/2021 21:17, 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.

Are there any conventions or effects that this goes against?

Good grief. It is *your* lounge, do with it what *you* want.
Just be sure to call it a wall of colour to keep it politically correct.