We measured the increase in reading speed afforded by two currently available systems of coloured overlays: the "Intuitive Overlays," which provide a choice of 30 colours, and the "Eye Level Reading Rulers," which provide a choice of 5. Forty-eight pupils from a local authority primary school who reported experiencing symptoms of visual stress were individually tested with both systems in a random order, balanced across pupils. There were no differences between the systems as regards the children's preference or the reduction in symptoms of visual stress. However, there was a significant increase in reading speed with the "Intuitive Overlays" and no increase, on average, with the "Reading Rulers." Pupils showing an increase in reading speed of more than 5% with either overlay were tested again, on this occasion with "Intuitive Overlays" of the conventional size and those cut to the (much smaller) size of the "Reading Rulers." There was no difference in reading speed between the large and small overlays. Participants whose reading speed increased with the "Reading Rulers" by as much as with the "Intuitive Overlays" tended to be those who chose a similar colour for both overlays. The general pattern of results suggests that the "Reading Rulers" failed to increase reading speed because they do not offer sufficient colours and hence the benefits of the "Reading Rulers" in increasing reading speed are likely to be less than obtained with the "Intuitive Overlays."