What is red-green colour vision deficiency?
- Part of the eye
- Long & medium wavelengths
- Group
- Colour vision
- Vision functions involved
- Colour
- Main source
- RNIB
Protan types affect the long-wavelength cone signals. Deutan types affect the medium-wavelength signals. There are milder and more marked forms. The exact colours which cause trouble depend on the person, the shade and the lighting.
Optometrist
An eye-care professional who tests sight, checks eye health and can refer you for specialist care.
How red-green colour vision deficiency can affect day-to-day life
You may recognise some of these situations, or none of them. The point is to find help with the things you want to do.
Status lights
Red and green alone may not clearly communicate a device's state.
Choose a text status or an accompanying icon.
Team games
Some kit combinations may be difficult to distinguish.
Agree contrasting patterns or clearly numbered bibs.
Spreadsheets
Colour-only 'good' and 'bad' cells can hide their meaning.
Show the value, a label or a symbol in each cell.
Changes you may notice
- Some reds, greens or browns can be difficult to separate.
- Other combinations, including some blues and purples, can be confusing too. No single list applies to everyone.
Everyone is different. Symptoms on their own cannot identify a condition.
What to do about a new or sudden changeAssessment and care
An optometrist can assess colour vision and explain the result. Inherited red-green deficiency is generally stable. A new or worsening colour change should be checked rather than assumed to be the inherited type.
Names you may hear
Protanomaly and deuteranomaly describe altered cone responses. Protanopia and deuteranopia describe the absence of the corresponding cone function. None of these names mean every object of one colour disappears.
How vision is affected
These topics explain the parts of vision involved. They do not predict your sight, diagnose anything or show the condition itself.
Colour
Colour helps you tell things apart. Clear labels and patterns make the same information readable without relying on colour.
Open the colour labEveryday support
Common red-green deficiency does not usually reduce fine-detail vision. Colour filters do not restore typical colour vision, and no screen simulation establishes your type.
A question to take to your appointment
Can you explain my test result and any colour requirements for the work I want to do?Prepare your appointment checklist
Sources and review status
Sources checked 4 October 2026. Educational draft, not yet clinically reviewed. No clinician has endorsed this page. Follow the advice of your own eye-care team.
How this content is prepared