Pop quiz, hotshot. Where have you seen those colours before?

 

Too easy? Well try this on for size.

 

Oh, a wise guy eh? Well what about this?

 

Alright, alright, I’ll stop. As you obviously know, because that’s the kind of cool dude you are, those are the colour palettes used be three of the world’s most famous metro maps – the London Underground, Paris Metro and New York Subway respectively.

They come from the mildly mind-blowing Global Subway Spectrum, which catalogues the colours of every metro map in the world. It’s all the work of Chicago-based designer Nicholas Rougeux. Here’s his rather nifty explanation of his process.

Taken from Nicholas Rougeux’s Global Subway Spectrum. Click to expand. 

The position of the dots on each colour wheel represents the exact shade. Blues are bottom left, greens bottom right, reds at the top; the further from the centre, the darker the shade.

Here’s the full selection from metro maps worldwide:

 

The version on Rougeux’s site is actually interactive, so if you hover over a colour, this happens:

 

There’s loads of other stuff you can do with this tool. You can see, for example, that Africa hardly a has any metros:

That’s just three systems, in fact. But Asia has loads:

 

So does Europe:

 

You can also view all the colours in this attractive waterfall arrangement:

 

Or in this interactive 3D graphic, which we frankly have no good way of reproducing on CityMetric, but which is nonetheless very, very cool:

This looks better when it moves, to be honest. 

Lining all the colours up in one place like this highlights the fact that certain colours are more popular. The metro maps of the world are festooned with reds, blues and greens; but there are slightly fewer yellows and purples, even fewer pinks, browns and oranges, and a bare handful of greys.

Least common of all seems to be black, which features in just two networks (London and Bilbao), so if you got annoyed with the Northern Line this morning, take some comfort in the fact that it is in some way special.

Rougeux’s work highlights another point, too. In all, the site categorises 162 different metro networks, and by default it arranges them by the number of colours they use. I counted them, because I do that sort of thing. Here’s the distribution:

Of the 162 networks on the site, only 12 of them uses 10 or more colours, and no network uses more than Seoul, with 15.

Partly this result from the fact that so many metro networks are pretty simple things: 134 of them – the vast majority – get away with five colours or less.

But there’s something else going on here, too. The New York Subway has at least 24 lines (more, if you count the expresses separately); yet it only uses 10 colours.

It does this, I suspect, because a map which uses 24 different colours would not be comprehensible at first glance. You’d need to look carefully to make sure that the blue line you were on, and the one you wanted to get to, were the same blue line.

In other words, thanks to the limitations of both cartography, and the human eye, there is a limit on the number of colours a metro map can use before it gets confusing.

We discuss this on the latest edition of our podcast, incidentally – so you should probably subscribe.

You can find the Global Subway Spectrum here.

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