Are you sure the sky is blue?

The dreaded question by every parent – “why is the sky blue??”. It is a long-standing fact that the sky is classified as blue, but when it is put into question, this idea that has been so deeply ingrained in our brains begins to falter. Depending on so many factors, the sky can be garnished by so many other colors. This is especially true in terms of artwork and the abstraction that accompanies it. The constructs that we have grown up in have assigned very concrete terms to very abstract objects – without this, how would we begin to explain the color blue?

A Parisian sunset of orange, pink, purple, and lastly, blue.

As Norris notes in her review of Color in the Age of Impressionism (2019), artists such as Degas, Renoir, and Monet encouraged the use of brighter color palettes. Color became abstracted and independent – autonomized in a sense. This created a world in which color and object were not always married in comparison to those in the natural world…this became especially true in post-impressionism. Artists such as Van Gogh, Seurat, Cézanne, and Gauguin truly divorced color from form. In this case, the sky could be painted green but the context of the painting would still allow your mind to label it as the ‘sky’.

A Parisian rainstorm causing the sky to turn completely grey.

These painters began to venture into a more abstruse realm of color. Object-associated color is implicated in the left fusiform gyrus in the posterior temporal cortex; near here is also where color is perceived (Simmons et al., 2007). Through an fMRI study performed by the discussed paper, it was found that color knowledge is also stored in this area lending evidence to the theory that knowledge is contained in modality-specific brain regions (Simmons et al., 2007). In this case, color knowledge is stored where object recognition takes place. By this token, recognition of the sky in a painting stimulates both color knowledge and object-associated color simultaneously. This can be occasionally problematic when object-associated color does not match with color knowledge.

One of Monet’s many Water Lilies paintings that shows extreme abstraction of color where the ‘sky’ is magenta.

However, memory is also involved in the perception of color as it’s inherently involved in most everything we do (Hansen et al., 2006). These researchers asked participants to tweak the color of fruits until they appeared to be grey; this was typically when the grey point was manipulated to that of opposite the fruit’s natural color (Hansen et al., 2006). This demonstrates that perception of color is heavily regulated by visual memory. Seeing the sky as blue during a particularly beautiful day is not rare, it has been consolidated as a memory in the brain. Perceiving the sky as blue in a painting, therefore, is easy. Yet, a lime green sky is an incompatible scene to imagine. Therefore, the brain must use unconsciously use the surrounding context clues to fill in the gaps. Though we may not notice this, it is happening constantly within our minds to fill in small gaps within our world that may not make logical sense.

The Sower by Vincent van Gogh, November 1888 adorning a green sky.

The general question, “what color is the sky?” opened a can of worms in the visual perception of color from an artistic viewpoint. As I explore Paris and learn of all its history and artwork, many of the paintings request a second longer to interpret. This was true especially for paintings from the post-impressionism movement as seen at the Musée d’Orsay. The uncoupling of objects from their natural color removes the ability of memory archives to be used contributing to the beauty and allure of these paintings.


Hansen T, Olkkonen M, Walter S, Gegenfurtner KR (2006) Memory modulates color appearance. Nature Neuroscience 9:1367-1368. doi: 10.1038/nm17

Pope N (2019) Color in the age of impressionism: commerce, technology, and art by laura anne kalba (review). Technology and Culture 60(1):330-33. doi: 10.1353/tech.2019.0018

Simmons WK, Ramjee V, Beauchamp MS, McRae K, Martin A, Barsalou LW (2007) A common neural substrate for perceiving and knowing about color. Neuropsychologia 45(12):2802-2810. doi: 10.1016/j.neuropsychologia.2007.05.002

Van Gogh V. (1888) The Sower. [Painting]. Retrieved from

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