Short answer
Low vision usually means reduced contrast sensitivity, often with glare sensitivity, reduced colour discrimination and a narrowed field, and it becomes common with age. People affected need more luminance contrast than the WCAG minimum, often prefer to set their own text and background colours, and are hurt most by pale greys, glare and designs that break when colours are overridden. Designing above the thresholds and surviving user colour changes matter more than any one palette.
Low vision is vision loss that glasses or contact lenses do not correct and that affects everyday tasks. The W3C's draft on low-vision user needs describes several dimensions relevant to colour: contrast sensitivity (the ability to tell bright from dim areas, and so text from background), light sensitivity (bright screens causing pain or making text unreadable, leading some people to need dark backgrounds), colour perception, and field loss (central, peripheral or patchy). It also notes that from around age forty most people's vision declines — focusing, colour perception and contrast sensitivity all fall — even though many do not think of themselves as having a disability. A large and growing share of any audience is affected to some degree.
The W3C explains the 4.5:1 text threshold as compensating for the loss of contrast sensitivity that typically accompanies visual acuity of about 20/40 — roughly the vision of people around eighty. The baseline of 3:1 is multiplied by a contrast-sensitivity loss of about 1.5. That makes 4.5:1 a floor designed with low vision in mind, not a comfortable target: people with more significant loss need more. WCAG's enhanced level asks 7:1 for the same reason. The practical guidance for designers is to treat 4.5:1 as the minimum for incidental text and aim for 7:1 or more for body copy and anything people read at length.
WCAG ratios are computed from colour values, and the formula's +0.05 terms stand in for a little ambient flare. Real screens in real rooms reflect more. Reflected light adds roughly the same luminance to both text and background, which reduces the ratio — and reduces it most for pairs that were only just passing. The table applies a simple veiling-glare model. A #767676-on-white pair, just above 4.5:1 on paper, falls below it with a modest amount of added glare, while #595959 keeps a comfortable margin. Light text on a dark background is affected even more strongly, because the dark background's low luminance is swamped first. Glare sensitivity is common in low vision, so the people most affected by glare are also the ones who need the margin most.
The glare figures are a teaching model — a fixed luminance added to both colours — not a measurement of any screen. Real reflections depend on the panel's coating, brightness and the room.
Many people with low vision do not use a site's colours at all. They use operating-system high-contrast themes, browser extensions, reader modes, inverted colours or forced colours mode, which replaces author colours with a user-chosen palette. WCAG's AAA criterion 1.4.8 asks for a mechanism to let users select foreground and background colours, and its Understanding document notes that the combinations people choose can seem unintuitive to others. The design implications are concrete: never convey information with background images or colour alone (they are often removed), use real borders or outlines rather than shadows or background differences to show control boundaries, keep text as text rather than in images, and test in forced colours mode to see what survives.
| Pair | No glare | +2% | +5% | +10% | +20% |
|---|---|---|---|---|---|
| #595959 text on white | 7.00:1 | 6.29:1 | 5.50:1 | 4.60:1 | 3.57:1 |
| #767676 text on white | 4.54:1 | 4.26:1 | 3.91:1 | 3.47:1 | 2.89:1 |
| #949494 on white (3:1, borders) | 3.03:1 | 2.92:1 | 2.77:1 | 2.57:1 | 2.28:1 |
| #E0E0E0 text on #121212 | 14.19:1 | 10.72:1 | 7.97:1 | 5.73:1 | 3.88:1 |
Why: It sits just above 4.5:1, with no margin for reduced contrast sensitivity or glare.
Fix: Darken secondary text towards 7:1.
Why: Their boundaries were drawn with background colours or shadows that forced colours removes.
Fix: Draw boundaries with borders or outlines.
Why: It was conveyed by a background image or colour.
Fix: Put the information in text.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
StandardStrong evidence
The W3C explains WCAG's 4.5:1 text-contrast threshold as compensating for the contrast-sensitivity loss of about 1.5 typically associated with 20/40 visual acuity, applied to a baseline of 3:1.
Source: Understanding Success Criterion 1.4.3: Contrast (Minimum) (WCAG 2.2)
FactModerate evidence
The W3C's draft on low-vision user needs describes contrast sensitivity, light sensitivity, colour perception and field loss as dimensions of low vision, and notes that from around age forty most people's vision declines.
Caveat: The document is a 2016 First Public Working Draft describing needs, not requirements.
Source: Accessibility Requirements for People with Low Vision
StandardStrong evidence
WCAG 2.2 criterion 1.4.8 (Level AAA) calls for a mechanism by which users can select foreground and background colours, because some people with visual or cognitive disabilities need specific colour combinations.
Source: Web Content Accessibility Guidelines (WCAG) 2.2; Understanding Success Criterion 1.4.8: Visual Presentation (WCAG 2.2)
Colourwise analysisModerate evidence
Under a simple model in which reflected light adds the same luminance to text and background, a text pair just above 4.5:1 falls below it with modest glare, while a pair near 7:1 keeps a margin.
Based on: Computed by Colourwise by adding a fixed luminance to both colours in the WCAG contrast formula; see the table.
Caveat: A teaching model, not a measurement of any display or room.
Source: Web Content Accessibility Guidelines (WCAG) 2.2; Understanding Success Criterion 1.4.3: Contrast (Minimum) (WCAG 2.2)
FactStrong evidence
In forced colors mode the browser replaces author colours for many properties with a user-preferred palette, which can remove background colours and images that a design relied on.
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.