Colour Blindness in Orienteering

How many times have those of us who suffer from colour blindness stared at our map after the race and said “If only …..”: a different overprint had been used, a control number shifted a little bit onto a different background, the dark green on the map not quite so dark, etc

09th Jun 14

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Here, Adam Hunter explains some of the science behind colour blindness and its implications for orienteering, and Ian Maxwell and Roger Scrutton provide some first-hand accounts. Adam has worked as a sport scientist for elite athletes for more than 10 years, and enjoys orienteering, running and mountain biking.

Colour blindness is a common term used for colour vision deficiency. However, true colour blindness, where no colour can be seen at all, is rare. Colour vision deficiency affects around 8% of men and 0.5% of women. Most people with colour vision deficiency inherit the condition from their parents. However, it can also develop as a result of a pre-existing health condition or as a side effect of a medicine.

Inherited colour vision deficiency occurs due to an abnormality in the retina (the film that lines the back of the eye). The retina is made of rod and cone cells. There are three main types of cone cells (Red, Green, Blue). In people with inherited colour deficiency, one type of cone cell is missing or does not function normally. This results in not being able to see colours clearly and accurately, and difficulty in distinguishing between different colours.

There are two main types of colour vision deficiency:
1) red-green – the most commonly inherited type where people are unable to distinguish between certain shades of red and green;
2) blue-yellow – this is a very rare condition (usually as a result of eye disease in the elderly). It is difficult to distinguish between blue and green and yellow may appear as a pale grey or purple.

Colour vision deficiency varies in severity from very mild to severe. In addition, the ability to detect colour saturation varies from ‘anomalous’, where colours are only confused in the lighter pastel shades, to ‘opia’, where colours cannot be differentiated even when relatively saturated. Therefore, any two colour-defective people are unlikely to have identical difficulties interpreting colours.

There is currently no cure for inherited colour vision deficiency, because it is not possible to repair or replace the cone cells in the retina. As colour-defective vision affects almost 8% of males and 0.5% of females, if orienteering seeks to increase participation, consideration should be given to how we can improve the experience of those affected. In orienteering, colour-defective vision results in the coloured symbols used on the map becoming more difficult to differentiate (see picture).  Ian Maxwell describes this: “I can't tell the difference between a knoll, boulder or small thicket on the map, which can cause issues when I don't read the control descriptions; different coloured Xs for rootstocks, trees, etc look the same to me and I have mistaken form lines for paths. Vegetation is also a problem with white on open ground (e.g. small groups of trees) being hard to spot, and I cannot tell colours under a marsh. As a result I tend not to navigate by vegetation and try to use other features and contours.”

Due to the large variation in condition it would be difficult to obtain a single standard which was optimal for all variations. However, the map could be optimised to assist the most common variations Deutan and Protan (red / green confusion). The IOF have in the past made changes to the colours used such as the purple / pink used for course markings to try to improve the readability by people with colour-defective vision. However, it has been suggested that more could be done in the way of differentiating different colours with different patterns as well.

Roger says, “My biggest problem is red/pink overprint on darker green. This is a particular problem in urban orienteering, when the olive green is printed in a dark shade and detail is very important for navigation. A dark grey background can also be a problem. Purple overprint is better. A white edging to the control numbers also helps”.

Ian says, “Depending on what shade of red is used, the course overprint (including control circles and numbers) can be very hard to see, particularly in urban events over grey of buildings or olive green. I particularly enjoy these events, but cannot tell until I pick up the map whether I will be able to read it easily or struggle. I have developed a technique of following the lines back to their intersection point to tell where controls are and do this almost intuitively now. Unfortunately I also have a habit of missing controls or going to the wrong control on these events, where lines cross and confuse things. The course overprint should be easily sorted with a little bit of effort. (Some planners make a point of doing this and others put a white shadow around the numbers, which is a great help.)”

The second issue people with colour-defective vision are likely to face in orienteering is identifying a control flag in the forest. If the flag is against a green forest, the orange blends in, making it difficult to identify (see picture). Ian says, “I tend to pick out the white colour with the orange often not standing out against the background.” As a result, some clubs have put an additional blue stripe on the flag which helps a person with colour-defective vision identify the flag from the forest.

This is definitely something to think about if we are to be as inclusive as possible and increase participation in orienteering. You can see for yourself how your maps will look by downloading Color Oracle software. The challenge in making these changes is that all maps follow the international standard, so there would need to be a change in the standard and then every map would need updating to match that new standard.

In the picture, the top, left panel is what is seen with normal vision and the other three panels what might be seen under various colour vision deficiencies.

Examples of how colour blind people see colours

For more information see:
• Colour vision deficiency, www.nhs.uk/conditions/Colour-vision-deficiency/Pages/Introduction.aspx, by NHS.
• Color oracle v 1.2.1, colororacle.org by Jenny Bernhard
• Comments on how coloured maps might be seen by Orienteers with colour-defective vision, by Barbra Junghans.

Photo of authorPosted on 09th Jun 14
by Admin