Impossible Colours

Impossible Colours

by Jasmine Chan

 

Source: “Neon Bright Color Background.” Teahub.io, www.teahub.io/viewwp/iTTowxm_neon-colors-backgrounds-neon-bright-color-background/.

INTRODUCTION TO IMPOSSIBLE COLOURS

Impossible colours, how can they be… impossible? There are a variety of colours that we as humans cannot see due to how our eyes are developed. Colours are a concept that we have developed. Other organisms looking at the same thing may perceive the same thing we are looking at as a different colour. The colours we see are due to reflections of wavelengths of visible light. [1] 

HOW DO WE PERCEIVE COLOUR? 

Before I start talking about visible colours, I have to address how we perceive colour. In our human eyes, we have photoreceptors known as rods and cones, both found in the retina. Rods are the ones which are used for greyscale vision, whereas cones are used for coloured vision (which I will be focussing on in this topic). Cones have three types: red, green and blue. Each type of cone can detect a range of wavelength of light. Wavelengths of red, green and blue are the most sensitive to us, and hence, the cones are named after them. However, of course, other colours such as orange are possible due to the overlapping of the cones. The messages are overlapped, meaning that the colour sent to the brain would integrate, allowing us to see millions of colours. [2] For example, when light hits a banana, the banana absorbs most of the other wavelengths of light but reflects the yellow wavelengths. [3] Our eyes can see yellow as the red and green rods overlap and are stimulated, but the blue cones are not stimulated. [2] 

Fig.1 The Spectrum of Wavelengths of Photoreceptors in the Human Eye.

Source: Kazilek, CJ, and Kim Cooper. “Rods and Cones.” Arizona State University, 6 Jan. 2010, askabiologist.asu.edu/rods-and-cones. 

Fig.2 The Structure of the Human Eye.

Source: Pappas, Stephanie. “How Do We See Color?” LiveScience, 29 Apr. 2010, www.livescience.com/32559-why-do-we-see-in-color.html.

TYPES OF IMPOSSIBLE COLOURS

There are three types of impossible colours: forbidden, chimerical and imaginary colours. [4]

Forbidden colours are the type of colours that eyes cannot process at all. As our eyes work antagonistically, opposite colours cannot be seen, such as reddish-green or yellowish-blue. [4,5] (Note: opposite colours in the RBG spectrum differs from the RYB spectrum, which you may learn in art lessons.) This colour is seen as the visual cortex of the brain constructs this colour by mixing signals from different parts of one eye or from separate eyes. [6]

Fig.3 Types of Colour Spectrums.

Source: “The Colors of Graphic Design (Color Model History and Study).” Teknonics, 8 Oct. 2012, teknonics.wordpress.com/2012/10/06/the-colors-of-graphic-design-color-model-history-and-study/.

Try this with the examples below. Cross your eyes until the two crosses meet and are on top of one another. The colour in between you see should be the forbidden colour. 

Fig.4 Forbbiden Colours Example 1: Red and Green.

Source: Le Cunff, Anne-Laure. “Impossible Colors: Our Vision's Incomplete Palette.” Ness Labs, 15 Aug. 2020, nesslabs.com/impossible-colors. 

Fig.5 Forbbiden Colours Example 2: Blue and Yellow.

Source: Le Cunff, Anne-Laure. “Impossible Colors: Our Vision's Incomplete Palette.” Ness Labs, 15 Aug. 2020, nesslabs.com/impossible-colors. 

Chimerical colours cannot be seen directly, but it can be generated in the brain just by looking at two colours at the same time. This requires the cones to become fatigued when looking at a saturated colour, which then temporarily changes the colour sensitivities to the cones. [4] The photoreceptors in the retina do not refresh immediately, meaning that the message is still transmitting a few milliseconds after the stimulus is removed. This is why staring at something with a sharp contrast such as a lightbulb in a dark room can leave an imprinted image in our visions when we look away from the source of contrasting stimuli. This method to see chimerical colours works since when the photoreceptors consistently send the same message to the brain (for example, staring at a colour for an extended period of time), our brains would stop paying attention to the stimuli and causes our eyes to develop a temporarily, very short-lived blindness. [7] 

Fig.6 Example of a Lightbulb in a Dark Room.

Source: Hastings, Kirsten. “Light Bulb on Dark Background.” International Adviser, 16 July 2018, international-adviser.com/seven-steps-for-better-platform-client-outcomes/light-bulb-on-dark-background/.

There are three types of chimerical colours: self-luminous, stygian and hyperbolic. [6] Self-luminous colours are colours that seem to glow even when there is no light emitted from the stimuli. This can be seen after staring at a green background for a minute, then to a white background. When the green cones are fatigued, a red after-image is produced (opposite colours). This causes the red produced to seem like it is glowing as if it was brighter than white. Stygian colours are saturated and dark. This colour can be seen by staring at a bright yellow background then to a black background. The resulting colour is dark blue which seems as dark as black but coloured. This colour can appear as specific neurones in the eyes only send signals when in the dark. Hyperbolic colours are very saturated. This can be seen after staring at an intense bright colour then to its complementary colour (red and green; blue and orange; yellow and purple). For example, after staring at a bright blue background then to an orange background, an oversaturated orange colour can be seen. [8]

Try using this template below. Stare at the cross for a minute or so, then stare at the cross at the target field.

Fig.6 Chimerical Colour Demo Templates.

Source: Helmenstine, Anne. “How Impossible Colors Work (And How to See Them).” Science Notes, 5 Aug. 2020, sciencenotes.org/impossible-colors-work-see/. 

Imaginary colours are known real colours that we can actually see but do not have a corresponding wavelength in the visible light spectrum. [4] The visible spectrum cannot correspond to all colours we see as we can perceive unsaturated colours - such as magenta, a mixture of red and blue wavelengths. [9] 

CONCLUSION

Impossible colours are incredibly interesting. Colours which are hidden in our daily lives make us appreciate more of our coloured eyesight. Using the visible light spectrum, there are no possible ways that we can incorporate these impossible colours into our daily lives. Maybe in the future, we would have technology which enhances our colour range... making our coloured vision even more interesting than it currently is.

BIBLIOGRAPHY

[1] Vyas, Kashyap. “Impossible Colors and How to Train Your Eyes to See Them.” Interesting Engineering, 2 May 2018, interestingengineering.com/impossible-colors-and-how-to-train-your-eyes-to-see-them. 

[2] Kazilek, CJ, and Kim Cooper. “Rods and Cones.” Arizona State University, 6 Jan. 2010, askabiologist.asu.edu/rods-and-cones. 

[3] “How Humans See In Color.” American Academy of Ophthalmology, 29 Sept. 2017, www.aao.org/eye-health/tips-prevention/how-humans-see-in-color. 

[4] Le Cunff, Anne-Laure. “Impossible Colors: Our Vision's Incomplete Palette.” Ness Labs, 15 Aug. 2020, nesslabs.com/impossible-colors. 

[5] Crane, Hewitt D., and Thomas P. Piantanida. “On Seeing Reddish Green and Yellowish Blue.” U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/17736657/. 

[6] Helmenstine, Anne. “How Impossible Colors Work (And How to See Them).” Science Notes, 5 Aug. 2020, sciencenotes.org/impossible-colors-work-see/. 

[7] “How To See Colors That Don't Exist.” Mental Floss, 23 Feb. 2017, www.mentalfloss.com/article/91138/how-see-colors-dont-exist. 

[8] Helmenstine, Anne Marie. “The ‘Impossible Colors’ Your Brain Sees but Your Eyes Can't Perceive.” ThoughtCo, www.thoughtco.com/impossible-colors-introduction-4152091. 

[9] Helmenstine, Anne Marie. “The Visible Spectrum: Wavelengths and Colors.” ThoughtCo, www.thoughtco.com/understand-the-visible-spectrum-608329.