Colour by number with a colour vision deficiency
The picture is indexed by number, and a number is text — so the task can be completed without telling any two colours apart. The friction is in the palette strip and in cues carried by colour alone.
You have spent your life being told you get colours wrong, and a pastime whose name is literally a colour looks like an obvious one to skip. It is worth a second look, because of a structural detail that most descriptions of the activity never bother to mention: the picture is not indexed by colour. It is indexed by number.
Why the numbers change the problem
A number is text. Reading it uses none of the machinery that separates red from green. Region 7 is region 7 whether or not the seventh swatch looks like the third, and if you fill every region marked 7 with whatever the palette calls colour 7, the finished picture is correct — not approximately correct, exactly correct, identical region for region to the one somebody with typical colour vision would produce. The whole task can be completed without discriminating a single pair of colours.
That is genuinely unusual. Most visual pastimes fail quietly for people with a colour vision deficiency, because the instruction is embedded in the colour itself. Here it is written down beside the region in symbols, and the colour is only the output.
Where the friction actually is
Telling two swatches apart in the palette
The palette strip is the one place where colour does carry meaning. It is usually a row of coloured circles or squares with numbers on or beside them, and if two of those look identical to you, choosing the one you want becomes an exercise in counting positions rather than looking. That is workable, but it is tiring, and it goes wrong the moment the strip reorders itself or hides colours you have already finished.
The habit that fixes it is one sentence: trust the number over the swatch, every time. If the label says 9 and the circle looks like the one you had filed as 4, the label is right. That sounds too obvious to need saying and is surprisingly hard to do, because the eye is faster than the reading and gets there first.
Cues carried by colour alone
The second friction is highlighting. Most apps mark the regions belonging to the currently selected colour, and that is the single most useful thing in the genre — it turns a search through hundreds of small digits into something you can see at a glance. But if the marking is done purely by tinting those regions, and the tint sits close to something else on screen, the cue quietly stops working for you.
Some apps offer alternative highlight styles: a checkerboard, a pattern, a pulsing outline. Where that setting exists it is the first one to change, because a pattern is not a colour and survives any deficiency intact. The same goes for anything else conveyed by tinting — given a choice between a colour cue and a shape or pattern cue, take the one that is not colour.
The deficiency families, briefly
It helps to know roughly what you are working with, stated without more precision than a web page can honestly offer.
- Red-green deficiencies are by a wide margin the most common family, and they are what most people mean by colour blindness. Reds, greens, browns and oranges converge to varying degrees, and severity ranges from barely noticeable to substantial.
- Blue-yellow deficiencies are considerably rarer. Blues and greens can be hard to separate, and so can yellows and pinks.
- Seeing no colour at all — lightness only — is very rare, and generally comes with other visual effects that matter a great deal more than a colouring app does.
Two things follow. Experience varies enormously between individuals, including between two people carrying the same label, so advice written for a category is only ever approximate for a person. And none of this is diagnostic: if you have never been tested and are curious, an optometrist can settle it in a few minutes. A colouring app cannot, and nothing here should be read as an assessment of your vision.
Practical adjustments
- Try the colour filters your phone or tablet already has. Both major mobile systems ship display filters intended for colour vision deficiency, with a choice of type and an intensity slider, in the accessibility settings. They are worth ten minutes of experimenting even if you dismissed them years ago, because the intensity control does most of the work and most people leave it at the default.
- Put the filter on a shortcut. Both systems can bind one to a triple-press of a side button, so it becomes something you flick on for the palette strip and off again.
- Choose artwork with widely separated hues. A picture built from a dozen shades of one family is the hard case for everyone and the impossible case for some; one that ranges across the spectrum gives you lightness and position differences to work with as well.
- Work one colour at a time across the whole picture. Beyond being the fastest route through any picture, it collapses the number of times you have to pick from the palette at all — one decision per colour instead of one per region.
- Find your work with the highlight rather than the swatch. The highlight tells you where to go; the swatch only tells you what you already know from the number.
What is genuinely lost
An honest note to finish on. The finished picture will be correct, but whether it looks good to you is a separate question and not one anyone else can answer for you. If a palette was designed around a red-green contrast, the effect its designer intended is not the effect you will get, and no setting recovers it.
Some people find that makes the exercise pointless, and that is a reasonable conclusion. Others find that what they came for was the ordering and the slow completion, and that the palette was always incidental. There is no way to know which you are without trying one picture.
Frequently asked questions
Can I finish a colour by number picture if I am red-green colour blind?
Yes, and the result will be exactly right rather than approximately right. Every region carries a digit and the palette is indexed by the same digits, so the task is a matching exercise on text. You never have to judge whether two colours are the same.
What is the hardest part in practice?
Picking the intended colour out of the palette strip when two swatches look identical to you, and losing highlight cues that are conveyed by tint alone. The fixes are to read the number rather than look at the swatch, and to switch to a pattern-based highlight style if the app offers one.
Do the accessibility colour filters on a phone help?
Often, and they are underused because people try the default intensity once and give up. The intensity slider matters more than the filter type for most people. Binding the filter to a triple-press shortcut lets you use it only for the palette rather than all day.
Can a colouring app tell me whether I am colour blind?
No. Difficulty separating two swatches in an app is not a test — screen calibration, brightness, ambient light and the specific palette all affect it. If you want to know, an optometrist can test you properly in a few minutes.
Try it on a real canvas
Numbrush is colour by number for adults: mandalas, rose windows and geometric pattern work, twelve colours a picture, a magnifier for the tight spots, and a wrong tap that costs you nothing. Free, offline, no ads and no account.