Use screen masking to apply a coloured screen tint to the whole screen. To use screen masking, toggle on the 'Show Screen Mask' button and choose your desired colour. Once you choose your colour the screen will be tinted. Click on another colour to change it.
You can also choose a custom colour by clicking on the 'Custom' box. You can change the level of opacity by using the 'Opacity' + and - buttons. To turn off screen mask, and reset to default, toggle off the 'Show Screen Mask' button.