Light,Shadow: My Cube is beige instead of white

In the main menu, select Window > Rendering > Lighting Settings The Lighting window will appear. Inside it, under the first tab Scene, the first section Environment, Find the Sun Source option, and choose the directional light in your scene that should represent the sun (by drag-and-drop from the hierarchy window).

At the bottom, there is an Auto-Generate checkbox and a Generate Lighting button. Select Auto-Generate to bake lighting automatically after every change. Or click the Generate Lighting button to bake lighting once.

plus, you can select the "directional light" (the little "sun" in your scene) and change it's color too