How to change the color of the screen??

I have a slider and I’d really like to Know how to change, for example the r component of the general color in my game, just like a setting, for example making it all red or black.
Thus I think I should use Color.r,g,b,a , but it seems not working. Please, help me !!

Color.r = GUILayout.HorizontalSlider(red,0.0, 100.0);		


 Camera.main.backgroundColor.r = GUILayout.HorizontalSlider(Camera.main.backgroundColor.r, 0.0, 100.0);

I think you want post process effects. If that’s what you want, you need Pro version of Unity.

If you want an overlay to the screen, I advise trying out some tinted transparency materials on a plane and attaching that as a children of the camera