Blue is an ambiguous colour. Perhaps it is the least iridescent colour. One may find this statement silly, yet this view is based on comparative experiences of the blue. Although blue leaves a strong impression on us and entrances us inexpressibly, it often fades without leaving a trace. As Ōnishi noted about blue, or lapis lazuli respectively: "Although the existence of blue as such roots in the material principle, this does not apply to lapis [lazuli]. It is a matter but at the same time not a matter. My interest in this is the reason why I persistently stay with lapis [lazuli] in my work." Blue settles between matter and immatter, or between being and nothingness. Ōnishi had worked intensively with lapis lazuli since his expedition to Afghanistan in 2002, and in his work with lapis lazuli he expressed this contradictory dynamism of the blue. Similar to Ōnishi’s experience, almost two centuries earlier Johann Wolfgang von Goethe had already described blue as "a lovely nothing."

It is not easy to understand such a statement as it challenges our cognition and our common sense. One thinks that we see the blue clearly and that it undoubtedly exists. In fact, one can certainly find blue objects all around oneself without any effort. Alone by looking up, one sees the blue of the sky, which is our most representative experience of the blue. Despite this familiarity, the sky’s blue is not easily comprehensible. We live in a milieu in which the word and the concept of the blue have already been informed by scientific research. However, the recognition of the blue colour of the sky, or sky-blue, is not self-evident if one stands outside this intensely structured cultural environment.

According to the British politician and Homer scholar William Ewart Gladstone (1809–1898), the ancient Greeks lacked the blue of the sky. Gladstone exhaustively examined the usage of colour words in Homer's writings and found that therein the sky was never described as blue. Moreover, the word κυάνεος (kyaneos), which is applied to represent blue, does not singularly denote blue, but encompasses also black or brown etc. From this word only the meaning of darkness can be extracted. Without question, the ancient Greeks could accurately perceive the colour of the sky. But it is not clear whether they actually perceived the sky as blue.
This is not about language or the cultural settings: The Greeks simply did not have a complexly stratified language at that time, which is why they lacked a word that expressed the colour of the sky. Seen from this perspective, one understands that the knowledge of colour only emerges through cultural or linguistic structuring. Although colour words indeed carry social meanings, this does not mean that colour is only a sign within the communicative network.
Blue is recognised through activity. In 1789, Horace-Bénédict de Saussure described the application of his cyanometer, a circular paper device upon which he had painted the shades of blue divided into 53 segments. With this cyanometer, he tried to measure the shading hues of the sky in proportion to the amount of water vapour in the air or to the height of a mountain, respectively. During his expedition into the Alps, de Saussure noticed how blue the sky is and how its colour changes. Prior to the invention of the cyanometer, Prussian blue had been discovered. This first synthetic pigment of modern times made the creation of the cyanometer possible. Blueness as an object of knowledge was discovered only through an action. Without mountaineering, one would not know what sky-blue is like.

If it is not an object of deed, there is no need of recognising it, just like the blue in ancient times. Ōnishi's expedition to Afghanistan and his refinement of lapis lazuli opened his eyes through the encounter with the ancient stone and lead him to the discovery of blueness. Thus, little by little, blue is recreated again and again. It is not a permanent matter or a fixed concept. Blue exists in the becoming, in the dynamic contradiction. As Ōnishi recognized: "as if being born, as if rising up / the image of colour."