My models are black in the material preview and render view. The problem arised when I turned on my project. Everything worked before. I added the screenshot below.
You probably opened the scene world and here is how to close it: at the top right you have 3 viewports and at the right of them, there is an arrow points down, click it and there should be scene lights and scene worlds. You need to close all of them. If your problem something like I think, that will solve it.
And btw you need to add lights to show colours on rendering.