What colour are the Liberal Democrats?

There are many mysteries in British politics: What was the fate of the murderous Lord Lucan? What did Tony Blair and Gordon Brown agree at the Granita restaurant? Why do we continue to tolerate an electoral system that leads to minority rule?

And perhaps the deepest mystery of all: What colour are the Liberal Democrats? Polling company YouGov asked 2,096 British adults this pressing question during the 2024 general election campaign. The public were split, and Liberal Democrat voters even more so:

Yellow 55%, Orange 41%, Don’t Know 4%, with an arrow labelled “Can’t win here” pointing at the 4% Yellow Orange Don’t know 55% 41% 4% Can’t win here!

What do the Liberal Democrats say?

I checked with the Liberal Democrats, who were excited to have someone paying attention to them. They describe their primary colours as “charcoal and yellow”, which seems to settle the matter. They also helpfully provide three colour references for the yellow: Pantone 1375 C, CMYK 0% 38% 90% 0%, and RGB 255 159 26. Here’s Pantone’s colour swatch for that colour:

Hmm… that looks a bit orange to me. What about those RGB and CMYK references?

Light and ink

We’re able to perceive a spectrum of colours, ranging from red to violet, known as visible light. Three types of cell in our eyes are each sensitive to different parts of the spectrum, and combinations of lights that stimulate the three types of cell in the same way will appear to be the same colour.

Digital displays take advantage of this by producing three specific colours chosen to stimulate the different cells: the red, green, and blue of the RGB colour model. Other colours can be produced by starting with black and adding different amounts of red, green, and blue:

Ink doesn’t produce light, but absorbs it. To produce a wide range of colours we start with white and then add different amounts of inks that absorb red, green, and blue light. These are the cyan, magenta, and yellow of the CMYK colour model:

The Liberal Democrats’ colour is specified as CMYK 0% 38% 90% 0%. This means it’s created by combining 90% of the maximum amount of yellow ink with 38% of the maximum amount of magenta ink. Combining equal amounts of yellow and magenta inks produces red, so the Liberal Democrats’ colour, with much more yellow than magenta, can accurately be described as a kind of yellow-red. We should have a word for that.

What even is orange, anyway?

Orange is unusual among the major colours in that it was named comparatively recently. While the words for yellow and red date back thousands of years to the Proto-Indo-European language, in Old English the colour we know as orange was called ġeolurēad — literally yellow-red.

Meanwhile, East Asian farmers had cross-bred the pomelo and mandarin to produce a new citrus fruit, the nāram. It spread westwards until the Moors, who called it nāranj, introduced it to the Iberian Peninsula. It became known to the English elite by its Old French name pomme d’orange, and in 1502 some fabric purchased for Margaret Tudor’s marriage to King James IV of Scotland was described as orange — the earliest recorded use of orange as a colour in English.

With orange-the-colour being named after orange-the-fruit, we have a prototypical reference for what the colour looks like. The Liberal Democrats’ colour is in this picture and they don’t like it:

Three oranges arranged in a triangle with a half-orange balanced on top

What do scientists say?

The spectrum is a continuum from red to violet, but language is discrete, so we name the spectral colours red, orange, yellow, green, blue, and violet. Scientists associate these names with specific wavelengths of light. In the CRC Handbook of Fundamental Spectroscopic Correlation Charts, orange is defined as light with a wavelength between 590nm and 620nm.

The Liberal Democrats’ colour isn’t a pure spectral colour, but we can find a close match. By using the International Commission on Illumination’s colour matching functions we can convert a wavelength to a colour in the CIE XYZ colour space, and from there to the common SRGB colour space.

The end result is that the closest match is a wavelength of 609nm, corresponding to RGB 255 159 0 — an orange colour with a touch less blue than the Liberal Democrats’ colour. Top scientists agree: the Liberal Democrats are orange.