Well, white would of course be the best, with light brown whites and other colours are simply displayed incorrectly and you may have to readjust the colours, if that is possible to that extent. But I recommend a screen like this (frame or extendable)... LG
I would generally be careful with ultra-short distance beamers and walls. If there is rough plaster on it, the unevenness will cast shadows. I would generally buy a screen that is suitable for UST. The ViewSonic X-1000-4K can compensate for wall colour. The Xgimi does not have this feature, as far as I know.