The use of coloured overlays while reading can mitigate a range of visual perceptual problems, often collectively referred to as Meares-Irlen Syndrome, which is particularly prevalent in people with dyslexia.
Olive Meares in Australia was the first to suggest that children with visual reading difficulties can see print more easily through certain coloured filters. This was taken up commercially in the USA and UK.
While some sceptics still feel more research needs to be done in this area there are many practitioners who feel there are indeed real benefits associated with using coloured overlays with particular benefits associated with yellow and blue tones.
For further information : www.bdadyslexia.org.uk