I use coloured glasses when working with computers but our network has ssOverlay. which I can use if I forget them!   You can select the colour you want from settings arrow and activate the overlay.  It covers the screen completely and can be turned off and on from the bottom right of the taskbar. where a small yellow arrow can be seen.  Right hand mouse and you can exit the program. It is very simple and easy to use.

ssOverlay (921Kb download )
“Very similar to Dark Screen, ssOverlay (the ss stands for Scotopic Sensitivity), places a coloured overlay onto the screen. The colour and transparency levels can be adjusted to suit the user.”

Gloucester College student working on StemReader for Maths that has now been superseded by equation reading in Microsoft Word and TextHelp EquatIO