On 6 Mar 2021 at 21:17:32 GMT, "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?

There are no binding conventions and you are fully entitled to do it whichever
way looks good to you. But I think it is a little unfashionable among the
fashion police to have a contrasting wall colour at all, nowadays. A feature
thing in the middle of one wall is possibly the modern version?

--
Roger Hayter