Perhaps no other exhibit in the museum is quite as good at showing how your eyes can deceive you as the Colourless Room. Now, I know what you’re thinking — there is colour in here! Everything is bathed in a golden, sepia-like hue. But what’s interesting is what this unusual light does to your perception of colour.
Before we dive into it, there’s something important to understand: colour isn’t simply a property that exists on the surface of an object. It’s a perception created by your visual system.
Think about a red apple. The apple doesn’t contain “redness” in the way you might imagine. Instead, its surface reflects some wavelengths of light more strongly than others. The light that reaches your eyes is detected by specialised cells in your retina, and your visual system processes those signals to produce the experience of colour.
The light around us is part of the electromagnetic spectrum, which includes everything from radio waves to gamma rays. Humans can only detect a small portion of this spectrum: visible light, roughly from 400 to 700 nanometres. Different wavelengths contribute to the colours we perceive, but our experience of colour depends on much more than wavelength alone.
At the back of your eye are millions of light-sensitive cells called photoreceptors. There are two main types: rods, which are particularly important for vision in low light, and cones, which support detailed vision and colour perception.
Further along the visual system, cone signals are compared and combined into opponent colour channels. Broadly, these include red–green and blue–yellow relationships, alongside a light–dark channel.
So what happens in the Colourless Room?
The Colourless Room uses low-pressure sodium lamps, which produce light concentrated into two extremely close wavelengths around 589 nanometres. This makes the illumination appear almost monochromatic — essentially a very narrow band of yellow-orange light.
Normally, an object can reflect a broad mixture of wavelengths into your eyes. But under this lighting, there simply isn’t much of the rest of the visible spectrum available to reflect.
A blue object, for example, cannot reflect blue light if the lighting contains virtually no blue light. Instead, its appearance is determined largely by how much of the available yellow light it reflects. Objects that would normally look dramatically different in colour can therefore become difficult to distinguish from one another, appearing instead as different shades of yellow, orange, brown or black.
That’s why the room feels so strange: the objects haven’t changed colour — the light illuminating them has changed.
Walk into the Colourless Room wearing your brightest colours and watch them transform. The room isn’t filtering colour out of your eyes — it’s changing the light available for your visual system to interpret.