Beyond aesthetics, colour has an important functional role in wayfinding design.  Colour is often used to distinguish between floor levels, routes and different activity zones. For many people, colour offers a very clear and easy to follow intuitive cue to assist with navigation.

When creating a wayfinding strategy that uses colour as a navigation tool, we’re regularly asked about the suitability for people with colour blindness. With an estimated 8% of the male population and 0.5% of the female population worldwide having some degree of colour vision deficiency, this is a not an unreasonable challenge.

What is Colour Blindness

Colour blindness, or colour vision deficiency, is usually a genetic condition that affects the cone cells within the retina in the eye.  The cone cells contain photopigments, essentially sensors that detect light. There are three types – red, green, and blue – each sensitive to a specific wavelength range.  They work by sending messages to the brain which interprets these signals, enabling us to see a wide spectrum of colours.

An absence or deficiency in any one of these cell types will impact on our ability to distinguish between certain colours.  There are variations in degree of colour blindness with the most common form red – green and less frequently blue – yellow. Some people will only experience mild difficulties in differentiating between certain shades or hues. Whereas others will struggle to see the difference between a wider set of colours.

Good Practice in Design of Wayfinding Information 

Much of the guidance for designing for colour blindness, constitutes general good practice in sign design, top of the list is:

• Selecting a legible typeface;
• Avoiding the use of capital letters (except the first letter in a list or name);
• Using standard pictograms and simple language; and
• Ensuring the size of any text/graphics is appropriate to the viewing distance.

Guidance on Signage Design for Colour Blindness

While the above represent the basics for any wayfinding signage scheme, to meet the needs of wider range of stakeholders, including people with colour blindness, the design should also focus on:

Contrast – Ensuring high contrast between any content and the background i.e., use dark coloured text/graphics on a light background or vice versa. Although too stark a contrast such as white text on a black background can create legibility issues for some, with the edges appearing fuzzy (halation).

Colour combinations – Particularly pertinent for colour blindness, avoid using red and green to communicate different messages that could cause confusion. Using close variations in colour shades for distinguishing between floor levels, zones or routes (such as dark blue and purple; or pink and lilac) can be problematic for all. Associating different graphics, textures or patterns with colour is one mechanism for extending the range of options.

There are a range of online resources that will help you check colour combinations for different colour vision deficiencies. This is one that we’ve found useful and used in the past.

Use more than one cue – We all have different learning styles and preferences.  For some words or letters will resonate more strongly (and be more memorable), for others it may be images, numbers, or colours. Using a combination of colour with supporting text and or numbers or symbols to differentiate between floor levels or zones will help cover several bases.  However, if using more than one information cue, it’s critical that you don’t end up with so much content that it impacts on the overall legibility.

Ultimately, if in doubt, it’s recommended that the design is tested with a wide range of potential users. Large complex developments often have an accessibility consultant on the team. Or there may be a local accessibility group involved with the wider stakeholder engagement activities. Given that 8% of the male population are colour blind, there is a good chance there may even be a someone within the wider project team that can assist.