Coloured overlays and reading rulers: what they are, the evidence and how to choose

Coloured overlays are one of the most common things handed to a child who finds reading hard, and one of the most argued about. This guide sets out what they are, what the professional bodies say, and how people choose one, without pretending the question is settled.

What are coloured overlays and reading rulers?

A coloured overlay is a sheet of tinted, see-through plastic laid over a page; a reading ruler is a narrow strip of the same idea that covers a line or two.

Crossbow Education's A4 overlay covers a whole page. It comes in ten colours: yellow, sky, purple, pink, orange, magenta, jade, grass, celery and aqua. One side has a matt coating, which the seller says cuts reflected light while keeping print clear; the other side is gloss, and you use whichever you prefer.

Reading rulers do a smaller job. Laid on the page, they mark the line you are on and tint the text around it, which some people find easier to handle than a floppy A4 sheet.

There are screen versions too. Immersive Reader in Microsoft Edge has page colour themes, including some that Microsoft says are inspired by Irlen Spectral Filters, and a line focus that shows 1, 3 or 5 lines at a time. Chrome's Reading mode lets you change the colour theme, line spacing and letter spacing. Both are free.

What does the evidence say about coloured overlays?

It is mixed, and the professional bodies are cautious: they do not back overlays as a first step, and they are clear that overlays do not address dyslexia itself.

The British Dyslexia Association says coloured overlays and similar aids must not be promoted as the first strategy to help children with reading difficulties, and should not replace or discourage a full professional assessment. It mentions precision-coloured overlays or lenses in relation to pattern-related visual stress, which it describes as a separate matter from dyslexia. It says that dealing with visual difficulties is not the same as dealing with dyslexia, and that visual difficulties need diagnosing by qualified, registered professionals.

The College of Optometrists, the professional body for optometrists, says in its clinical guidance that claims about tinted lenses and visual stress remain controversial. It tells optometrists not to claim these interventions fix specific learning difficulties, and to explain that they carry a cost in money, time and raised expectations, because parents and patients might be open to the suggestion that anything may help. It points to proposed diagnostic criteria for visual stress, developed to reduce the risk of over-prescribing coloured filters.

The research. A 2016 systematic review of controlled trials by Bruce Evans and Peter Allen, in the Journal of Optometry, concluded that larger and more rigorous randomised controlled trials are needed, and that better diagnosis of visual stress is a priority.

So we make no claim that overlays or rulers make reading easier. We stock them because people ask for them, they cost about £5, and choosing one well is a reasonable thing to want help with.

How do people choose a coloured overlay?

By comparing several over the same text, in the same light, and keeping the one they prefer; there is no correct colour.

A sensible way to go about it:

1. Get an eye test first. The BDA advises a full assessment by a registered optometrist for anyone with visual difficulties when reading. It is free on the NHS for under-16s and for under-19s in full-time education.
2. Use the same page and the same light. A classroom under strip lights and a kitchen table in daylight will look different.
3. Compare two at a time. Lay two colours side by side over the same paragraph, keep the one you prefer, and bring in the next.
4. Try both sides. The matt side and the gloss side of the Crossbow overlay look different under bright lights.
5. Live with it for a couple of weeks. If you still reach for it without being reminded, that tells you something. If it ends up in a drawer, that tells you something too.
6. Try free screen tints first for digital reading. Edge and Chrome both offer colour themes at no cost.

Some optometrists offer a colour assessment. The College of Optometrists says any such intervention should come with clear communication about the limits of the evidence, so ask what the assessment involves and what it costs before you book.

Overlay, reading ruler or screen tint?

A full-page overlay for worksheets and books, a reading ruler for keeping your place, and a free screen tint for anything digital.

Can you use coloured overlays in exams?

Yes: JCQ lists coloured overlays among the arrangements that do not need an online application.

The same list in JCQ's Access Arrangements and Reasonable Adjustments for 2025 to 2026 includes exam papers printed on coloured paper or enlarged from A4 to A3, and read aloud, which can include an examination reading pen. These are set up by the school or college, so talk to the SENCo well before the exam season.

Things to know

• An eye test comes first. The BDA is firm that overlays should not replace a full professional assessment.
• Costs are not only money. The College of Optometrists warns about the time and raised expectations that come with any intervention. Five pounds is cheap; months of hope pinned on a colour is not.
• Crossbow's site did not load for us. We checked the overlay on Dyslexic.com. We could not confirm the reading ruler pack contents on 11 Sep 2026.
• Irlen. Microsoft names some of its page themes after Irlen Spectral Filters. That is Microsoft's description, not an endorsement from us or the bodies above.
• We have not tested these. Details come from the seller's and makers' pages, checked on 11 Sep 2026.