I found an excellent product for adding red screens to tables and smart phones, probably computer screens also.
Its very easy to lay over your screens and cut afterwards with a scissors. I leave enough space on my tables so I just fold the extra material back behind my tables, then add my cases to my tables to keep the edges in place. Touch screens are not effect by this material so your touch screen still is sensitive to your touch.
It also peels off easy to either reposition it or remove. It sticks well but doesn't leave residue, so save the paper you peeled of of it to store your screen once you're done using it. Long term use I cant comment on since I've only had this for a week so far.
If you need a darker red, you can add another layer, even several layers, and also dim you screens brightness. I just use one layer on my table for my Stellarium Star program but I use several layers on my second table that uses with my Excel spread sheet for my observing list.
You can push out bubbles with your finger if you get any, or use the supplied squeegee. In my case, bubbles don't effect me because I only use this at night under dark skies. I have two 10" tables i only use for astronomy one mounted on top of another on a small table tripod. I just need the red screen to preserve my night vision.
This is the tablet holder I use when I'm out with my gear and also, the second tablet holder I've attached below the first one.
The red screen is an excellent product!
Ralph / Sacramento