Comparing the effects of the colour and size of overlays

This is a summary of the peer-reviewed paper : "A comparison of the effects of the colour and size of coloured overlays on young children’s reading."

Original Paper Authors: Judith Veszeli (B.Sc., M.Sc.) and Alex J Shepherd (B.A., M.Sc. (Arch), Ph.D.) Department of Psychological Sciences, Birkbeck, University of London, London, UK

Publishing Journal: Vision Research (2019) 156, pp. 73-83

Summary by Elizabeth Macdonald.

Disclaimer: This summary serves as an overview of this paper and is in no way affiliated with the authors or in anyway endorsed or approved by them. Readers are encouraged to read the full paper for full details of the study and results. 


Coloured overlays and lenses have been reported to reduce perceptual distortions and visual stress experienced when viewing text, reduce fatigue, improve the clarity and comfort of text and so increase the speed of reading. 

This study compared the effects of the colour and size of reading aids, by measuring reading speed, reading errors, visual acuity and comfort. A sample of 106 children between the ages of 4-7 years old, over a wide range of reading levels, and who had not been identified as having learning difficulties or dyslexia, were assessed. This is a younger sample of children than has been tested previously.

This is the first study not only to compare the effects of colour on reading speed, but also to assess any impact it may have on visual acuity.

Two types of reading aid were used for the assessment; smaller reading rulers, which also have a tracking strip, and larger full page overlays. Reading performance was individually assessed with 10 different colours spaced evenly around the CIE (1976) uniform chromaticity diagram (a 2-D colour space). Two different, yet beneficial, colours were determined: the most effective and the clearest/most comfortable.


The study used a modified version of the Wilkins Rate of Reading Test, whereby short, high frequency words are read in a random order, to eliminate context and focus on reading speed and errors. All children were assessed prior to the test to ensure they were able to sight read all of the words used. The test was presented on a landscape page with two columns of text, to mimic an open book. The test paragraph of 60 words was embedded in the left hand column, where the reading aid was placed, so that simultaneous comparison could be made to the right hand page when the children judged clarity and comfort.

The group of children was divided in two, with half being assessed using page overlays and half using reading rulers. Both groups had comparable reading abilities.

The Test

For each child, a baseline reading speed was measured, which was the time taken to read 60 words with no reading aid.

10 separate tests then followed, using a different colour reading aid and a new paragraph of text each time.

For each assessment reading time (RT), errors and skipped words were recorded.

Once the tests were completed, the colours which the child found to be more comfortable to read with (if any) were compared sequentially side by side until the colour with the most comfortable viewing experience remained.

Once reading was completed, the child’s binocular near visual acuity was assessed using the Lighthouse LOGMAR near visual acuity chart. The chart was two sided, with different letters on each. The child was assessed using the most effective reading aid (that which generated the fastest speed and least errors; note this is not the same as the colour they deemed most subjectively comfortable), and also with no reading aid.

Key Results and Implications

All but 4 children had decreased reading time to some extent using a reading aid, compared to their baseline. Note that baseline RT vs fastest RT does not equal the slowest vs the fastest, as the slowest RT was not always found in baseline condition. 


Maximum decrease against baseline in RT using the most effective colour                 

Overlay Group Reading Ruler Group

  23.1 seconds        18.9 seconds

Average decrease against baseline in RT using most effective colour

Overlay Group Reading Ruler Group              

   8.3 seconds               7.8 seconds   

  (22% decrease)    (20% decrease)                                                                                                                                          

Maximum decrease against baseline in RT using the most comfortable colour

Overlay Group Reading Ruler Group

23.1 seconds          17.7 seconds

Average decrease against baseline in RT using the most comfortable colour   

Overlay Group Reading Ruler Group

6.1 seconds                    5.5 seconds

 (16% decrease)             (14% decrease)

Overall RT was faster with the most effective colour compared to most comfortable colour; however the size of the reading aid did not significantly affect the results.

The most effective colour also improved over a third of the children’s visual acuity. This has never previously been assessed.   “If the aids help with identification of letters (the acuity chart) and the reading of random words (the text passages), this early stage assistance may help subsequently with reading normal text: the flow of semantics, grammar and comprehension at later stages of reading would become a less taxing task.”.

In experiment 1 colours were assessed in the same order, and in experiment 2 a random presentation of colours was used.  However changes in RT vs baseline are distributed across the colours for each child, showing that it is unlikely that the most effective colour is due to familiarity or practice. It was also rare that the most effective colour corresponded with the child’s previously stated “favourite” colour.

The slowest RT was with no reading aid for only 15 of the overlay group and 8 of the reading ruler group, corresponding with previous research which dictates that coloured reading aids need to be individually determined for each child.

“Children regularly reported that, with certain colours, they see the text “properly” or made comments such as “wow, the letters got bigger!”, “the coloured side goes bigger” or “it lets me read”. “