I have a big problem in my scene. I have a texture in two different pieces. On my screenshot, wood texture is ok to left, but to right all the piece have this wood texture on roof and wall and the ambiant color become orange. Why ? Two hours i try to resolve that. Just directionnal light pass through a lightmass portal
It could depend on the lighting conditions. If you have the sunlight bouncing off a white surface, it would look like the left picture. If you have it bouncing off an orange surface, it might look more like the right picture.