Pink screen when opening Scenes.

When I try to open a pre-made scene in Unity the whole Scene window go’s pink, can anyone help?

I have included a screen-shot.

“Magenta” is the colour that Unity displays when there’s a problem with a material assigned to an object. It could be that it’s trying to use a shader that’s not supported by your graphics card, or there’s a texture missing, or some other error. Click on the object in question and look at its material in the inspector pane to find out more.

When I open the game exe I created, all the images, all the buttons and all the backgrounds are pink
Can you help me?