My model was working fine but randomly, all of my faces that are aiming directly up are turning many shades lighter than the rest of the faces. I am well versed in materials, reversing faces, shadows, styles, and SketchUp in general but this is stumping me. I have closed out of SketchUp and rebooted the app, reset the style to the default, reversed faces, added different materials on to the lighter sections, nothing.
Looks like you might have turned on Use Sun for Shading in the Shadow control panel.
That I did! Thank you. I found that also just adjusting the light and dark modes worked.
You should experiment with that a little more. Without shadows on or Use sun… turned on the illumination will appear to come from the camera. With one or the other on, you can adjust the Light and Dark sliders along with time and date to change how things look.