I’m using the samne materials for my walls and ceiling, so they should turn out pretty much the same color after building lights, but ceiling is yellow, should be white, wall is white, as per attached picture.
I’m indeed using a SkyLight with a Custom CubeMap. I ticked “Lower Hemisphere is Solid Color” and the ceiling color came back normal right away. I still need to build the lighhts, but I guess it will be fine. I did not find “Lower Hemisphere Is Black”, but I guess this is what you mean. How can I flag this as an answer ?
Oh yeah, Lower Hemisphere is Solid Color is the one. Disabling it(or setting it to a light colour) can help with dynamic exterior lighting to fake GI but it’s usually better to leave it black for interior archviz levels like yours.