On this page
What actually makes a colour?
Cambridge in Colour, a photography learning site, puts it simply: colour can only exist when three things are present, a viewer, an object and light. White light contains all the colours of the visible spectrum. When it hits an object, the object blocks some colours and reflects others, and only the reflected colours reach your eye.
Your eyes sense colour with cone cells. Cambridge in Colour explains that there are three types, each most sensitive to short, medium or long wavelengths of light, and the combination of signals from all three describes the range of colours we can see.
Why does a colour identifier give different answers in different light?
Because the light itself changes colour. Cambridge in Colour explains that light which looks white does not always contain an even mix of colours. It describes colour temperature, measured in kelvins: around 5000 K gives roughly neutral light, while 3000 K light leans orange and 9000 K light leans blue.
Our eyes are very good at judging what is white under different light sources. Cambridge in Colour notes that digital cameras often have great difficulty with auto white balance, and can create blue, orange or even green colour casts. So a white wall under a warm bulb can look white to you but slightly orange to the camera, and a colour name worked out from the camera’s picture will follow the camera, not your eye.
How can you get a more reliable reading?
These follow from how light and white balance work:
- Use one kind of light. Mixed daylight and lamp light gives the camera conflicting colour temperatures.
- Daylight is a good reference. Light around 5000 K is roughly neutral, according to Cambridge in Colour.
- Check twice. If the answer matters, look again in different light and see whether the name changes.
- Treat close shades as close. Two names that sit next to each other, such as a blue and a teal, may both be fair descriptions.
What if you think you see colours differently?
The NHS describes colour vision deficiency, often called colour blindness, as seeing colours differently from most people and having difficulty telling colours apart. You can be born with it, or it can start at any age.
The NHS advice is to go to an opticians if you or your child have signs of colour vision deficiency. It explains that the two main tests are the Ishihara test, which uses images made of coloured dots, and colour arrangement tests. Colour vision testing is not part of the routine NHS eye test, but you can ask your opticians for it. The NHS also says that although tests are available online, it is important to get checked at an opticians if you have concerns about your vision.
The NHS notes that colour vision can also be affected by some eye conditions, other health conditions and certain medicines. If your colour vision has changed, get it checked at an opticians.
An app like this can help with everyday tasks, but it cannot test, diagnose or treat anything about your eyesight.
Questions people ask
Is a colour identifier accurate?
It gives a reasonable everyday name, but the result depends on the light and the camera’s white balance, so treat it as a guide.
Why does my camera make white look blue or orange?
Cambridge in Colour explains that cameras often struggle with auto white balance and can add colour casts under different light.
How do I get tested for colour blindness?
The NHS says to go to an opticians. Colour vision testing is not part of the routine NHS eye test, but you can ask for it.
Where Colour Identifier helps, and where it does not
Colour Identifier is our Android app for naming colours. It names the colour under your camera and says it out loud, and you can tap anywhere on the picture to read a different spot. The names are about 40 everyday colour words, matched on a colour scale built to follow how people see differences. It runs on your phone, and no account is needed.
A one-time Pro unlock adds 849 detailed shade names and a white card: point the camera at plain white paper in the same light and the app corrects every reading for the tint of that light, which is the white balance problem described above. Pro also adds a way to compare two colours, a colour finder, and views that show how someone with red, green or blue colour blindness sees a scene. These views do not test, diagnose or treat colour vision.
What it is good for: quick, spoken colour names for everyday matching and describing.
What it will not do: under mixed or artificial lighting the name is approximate, and the camera’s auto white balance also shifts what it sees. It is not a lab colour measurement, and it is not an official app for any paint retailer. For paint, check a tester pot. For your eyesight, see an optician.
Questions or bugs: Email us.
Sources
- Color perceptionCambridge in Colour cambridgeincolour.com
- White balanceCambridge in Colour cambridgeincolour.com
- Colour vision deficiency (colour blindness)NHS nhs.uk