Colour overlays for reading: a practical guide for teachers

What colour overlays are and why they're used

Colour overlays are transparent coloured sheets placed over printed text to change the background colour the reader sees. They're one of the primary accommodations for visual stress (also known as Meares–Irlen syndrome) — a condition where the high contrast between black text and white paper causes text to appear to move, blur, shimmer, or flicker.

The theory behind overlays is straightforward. Lines of dark text on a light background create a repeating striped pattern, and for susceptible individuals this pattern triggers a form of neurological discomfort known as pattern glare. Changing the colour of the background reduces the contrast that drives this glare, making text appear more stable and comfortable to read. The overlay doesn't change the text itself — it changes the visual environment in which the text is perceived.

The evidence: Wilkins' research on pattern glare

Professor Arnold Wilkins at the University of Essex has conducted the most influential research in this area, spanning several decades. His key contributions have shaped how we understand and accommodate visual stress in educational settings.

First, Wilkins established the concept of pattern glare. Certain spatial frequencies — roughly 3 cycles per degree — cause discomfort and perceptual distortion in susceptible individuals. Lines of text on a page create exactly this kind of repeating pattern: dark stripes of text alternating with light gaps, repeated down the page. For most people this is unremarkable; for those with visual stress, it is enough to trigger cortical hyperexcitability that distorts what they see.

Second, Wilkins developed the Intuitive Colorimeter — a device that allows precise selection of the optimal colour for each individual. Unlike simply holding up a few coloured sheets, the Colorimeter can vary hue, saturation, and brightness independently, enabling fine-grained identification of the exact tint that provides maximum benefit.

Third, the Wilkins Rate of Reading Test provides an objective measure of whether a colour is actually helping. It measures reading speed with and without colour to identify individuals who genuinely benefit, rather than relying on subjective preference alone. His research shows that when the right colour is identified for an individual, reading speed can improve by 10–25%.

Key finding: colour preference is individual

This is the most important point for teachers to understand. There is no universal “best” colour for reading. What helps one pupil may make things worse for another. Some pupils read best with a yellow overlay, others with blue, pink, aqua, or green. The precise shade matters too — not just “blue” but the specific hue, saturation, and brightness.

This is why buying a random coloured overlay and giving it to a struggling reader isn't sufficient. A pupil who benefits from a pale rose overlay may find a deep pink one unhelpful or even counterproductive. The colour needs to be assessed individually, ideally using a systematic screening process with a full set of overlay samples, and confirmed with objective measures such as the Rate of Reading Test rather than simply asking the pupil which colour they “like best”.

Physical overlays: pros and cons

Physical overlays — the transparent coloured sheets you place directly on top of printed text — remain the most widely used form of colour accommodation in UK schools. They have genuine advantages:

• Cheap — a pack of overlays costs a few pounds, making them accessible for any school budget.
• Immediate — no technology required. A pupil can start using one within seconds of it being identified.
• Easy to try — pupils can test different colours quickly by swapping sheets during a screening session.
• Widely available — most educational suppliers stock them, and they can be ordered online.

However, in practice they come with significant limitations:

• They get lost, forgotten, left at home, or damaged — particularly with younger pupils. A teaching assistant who has spent time screening a pupil and identifying the right colour may find the overlay has disappeared within a fortnight.
• They only work on paper — no help with whiteboards, screens, or wall displays.
• They reduce light transmission, making text slightly dimmer, which can itself cause reading difficulty in poorly lit classrooms.
• The colour fades over time, especially with heavy use, meaning the overlay gradually becomes less effective without anyone noticing.
• Pupils may feel self-conscious using them, particularly in Key Stage 3 and above, where being visibly different from peers carries social cost.
• They don't solve the formatting issues that compound visual stress — small font, tight spacing, and dense layout remain problematic regardless of the overlay colour.

Digital alternatives

For screen-based reading, several digital options can replicate the effect of a physical overlay:

• Built-in OS accessibility features — Windows, macOS, iPads, and Chromebooks all have colour filter or tint options that can be applied system-wide.
• Browser extensions such as “Color Overlay” or “Visolve” that tint web content directly in the browser.
• Reading mode in browsers strips away formatting and allows background colour customisation, giving the pupil control over how text is displayed.
• Microsoft Immersive Reader has colour theme options built in, and is already available in many school Microsoft 365 deployments.

For printed worksheets — which still make up the majority of reading material in most classrooms — the most effective approach is building the tinted background directly into the document before printing. This means the colour is embedded in every copy and can't be lost, forgotten, or worn out.

The best approach for printed worksheets

Rather than printing on white paper and adding an overlay on top, the most reliable approach is to tint the background of the document itself. This way the pupil receives a worksheet that already has their preferred background colour built in.

The benefits are significant:

• The colour can't be lost or forgotten — it's part of the document.
• It's consistent across all materials the pupil receives.
• It feels less conspicuous than a coloured sheet placed on top of white paper, reducing the social cost for the pupil.
• It works for any document type — worksheets, reading passages, assessments, revision materials.

The challenge, of course, is that different pupils need different colours — which means creating multiple versions of every worksheet. If you have three pupils with visual stress in a single class, each needing a different background tint, you would need to produce three additional versions of every resource. This is exactly the kind of repetitive reformatting task that quickly becomes unsustainable to do manually, and is one of the reasons teachers often fall back on physical overlays despite their limitations.

How to find the right colour

Finding the right overlay colour for a pupil involves a structured screening process, not guesswork:

• Initial screening — Use a pack of coloured overlays (e.g., the Wilkins Overlay Screening set, which includes 10 colours). Have the pupil read a passage of text on white paper, then with each overlay in turn. Ask which (if any) makes the text more comfortable and stable. Time their reading speed with and without the preferred overlay using the Rate of Reading Test to get an objective measure.
• If overlays help — Refer for formal colorimetry assessment with an optometrist who uses the Intuitive Colorimeter. This can identify the precise tint the pupil needs — far more accurately than a set of 10 broad colours — and can lead to prescription precision-tinted lenses (glasses) for pupils who would benefit from colour correction throughout the day, not just when reading worksheets.
• Don't set and forget — Don't let a pupil self-select once and never revisit. Colour preferences can change over time, and the initial choice may not have been optimal. Review the overlay colour at least termly, particularly for younger pupils.

Overlays are one piece of the puzzle

Colour overlays address one aspect of visual stress, but they don't solve everything. A comprehensive approach to making text accessible addresses multiple factors simultaneously.

Font choice matters — sans serif fonts at adequate size (12–14pt minimum) are essential. Serif fonts add visual complexity that can exacerbate pattern glare. The BDA Dyslexia Style Guide recommends specific fonts and sizes that reduce reading barriers for dyslexic and visually stressed readers alike.

Line and letter spacing matter — cramped text is harder to read regardless of background colour. A minimum of 1.5 line spacing reduces the stripe-like pattern that triggers visual stress. Generous letter spacing prevents letters from crowding together and becoming harder to distinguish.

Layout matters — dense pages with too much text per section increase visual load. Breaking content into shorter sections with clear headings, generous margins, and adequate white space between elements all help. A beautifully tinted background won't help much if the text is set at 10pt in narrow columns with minimal spacing.

Overlays alone, without attention to these other factors, may give limited benefit. The greatest improvement comes when colour, font, spacing, and layout are addressed together as part of an integrated approach to accessible document design.

When to refer for formal colorimetry

Schools can and should do initial screening with overlay packs — this is well within the competence of a trained teaching assistant or SENCo. But formal diagnosis and the prescription of precision-tinted lenses require a specialist. Refer to an optometrist with experience in colorimetry (specifically one who uses the Intuitive Colorimeter, developed by Wilkins) if:

• A pupil consistently reads better with a coloured overlay during screening — particularly if the improvement is measurable on the Rate of Reading Test.
• The pupil reports that text moves, blurs, or shimmers without the overlay.
• Reading difficulties persist despite adequate phonics instruction and decoding skills — the pupil can decode when text is presented in a supportive format but struggles with standard black-on-white worksheets.
• The pupil experiences headaches or eye strain when reading, particularly during sustained reading tasks.

Not all optometrists offer colorimetry. The Society of Dyers and Colourists maintains a register of practitioners trained in the Intuitive Colorimeter system. Your local authority's SEND team may also be able to recommend practitioners in your area.

The scientific debate

It would be dishonest to present colour overlays without acknowledging the controversy surrounding them. The College of Optometrists has stated there is “no strong evidence” that coloured overlays are effective treatments for reading difficulties. Some researchers argue the benefits observed in studies are attributable to placebo effects or Hawthorne effects — pupils read better because they feel they're being given special attention, not because the colour itself makes a difference.

Henderson et al. (2018) conducted a systematic review of the evidence and found that study quality was generally low, with mixed results across the literature. Some studies showed clear benefits; others found no effect. Methodological issues — small sample sizes, lack of proper controls, inconsistent outcome measures — made it difficult to draw firm conclusions.

However, Wilkins and colleagues argue that the research shows clear benefits for the specific subset of individuals who demonstrate improvement on the Rate of Reading Test. They contend that much of the controversy arises from studies that don't properly identify this subset — giving overlays to all struggling readers (most of whom don't have visual stress) and then concluding that overlays don't work, when the real finding is that they don't work for readers who didn't need them in the first place.

The practical position for teachers is this: overlays are low-cost and carry no risk. If a pupil reads measurably better with one — faster, with fewer errors, with less fatigue — then the mechanism matters less than the outcome. You do not need to wait for the scientific consensus to fully resolve before making a simple, reversible accommodation that a pupil finds genuinely helpful. What matters is that the accommodation is based on proper screening rather than guesswork, that the colour is matched to the individual pupil, and that overlays are not used as a substitute for addressing other reading difficulties — a coloured overlay will not teach a pupil to decode, but it may make the page stable enough for decoding instruction to take hold.