Software Screen Tinting, or Colour Overlay for Mac Users with Dyslexia There are students at the school I work at who are dyslexic, and have the specific strand of dyslexia which doesn't deal well with black text on a white background. One way you overcome this with print is you put a coloured film over the text you're reading - and it really amazing how it improves their comprehension and their fluency (you can see an example of the overlay here).

I'm looking for a way to 'tint' the screen with software in the same manner on the mac. There is a windows solution, and a paid solution, but I'm looking for a free, cheap or built in way to achieve the same result. I've googled, and found a couple discussions but no solution. 

Are any of you aware of any software or system preferences I can use to either: 


tint the whole screen a colour (ideal)
change the background colour of windows / documents to one similar to the tint (better than nothing)
achieve a comparable result. 


If you have dyslexia and have found a workaround for this challenge I'd be really grateful for your input as well!

I thought that this would be achievable with the color setting in System Preferences but I don't think it allows the tinting sense. I might be wrong though. 

Thanks for your help!
I would suggest that you look at Nocturne:  



It allows you to invert the screen colors and create a night mode, which is much easier on the eyes.  It is also under the apache license, so open source and free to use.